Paleo Diet

Diet Reference Archive: a diet

Paleo Diet

A way of eating built on meat, fish, eggs, vegetables, fruit and nuts that leaves out grains, dairy foods, legumes, added sugar, added salt and processed foods. Its promoters say it matches the food humans evolved on before farming and that it prevents the chronic diseases of modern life.

Family: Low-carbohydrate and high-protein diets Promoted by: Loren Cordain and The Paleo Diet company, building on work by S. Boyd Eaton and Melvin Konner First appeared: 1985 in the medical literature; 2002 as a popular book GRADE: Moderate for short-term changes in waist circumference and triglycerides in adults with at least one feature of the metabolic syndrome, paleo diets against guideline-based diets, up to 6 months; published review (Manheimer et al., 2015)

ON THIS PAGE

1. In brief
2. Overview
3. In practice
4. For the coach
5. The evidence (opens on request)
6. Mechanisms (opens on request)
7. Risks, contraindications and myths (opens on request)
8. Key terms
9. Review questions
10. References
11. Evidence rating and review record

The summary and sections 1 to 3 are the short version and are open when the page loads. Sections 4 to 6 hold the research detail, the biology, and the cautions. Each of those opens when you select its heading, and you can read the page without opening them. Back to the Diet Reference Archive index.

In brief

What is it? A way of eating modeled on what its promoters believe people ate before farming began: meat, fish, eggs, vegetables, fruit and nuts, with no grains, dairy foods, beans or lentils, added sugar, added salt or processed foods. There is no single official version, and the versions people follow differ.

Does it work? Small, short trials, most of them in people who already had weight or blood sugar problems, found that people told to eat this way lost a little more from their waist and had a larger fall in triglycerides, a blood fat, than people told to follow their country's healthy eating guidance. A published review rated that evidence moderate in certainty for changes over up to 6 months. The longest trial, 2 years in 70 women, found that most of the differences between the diets had faded by the end.

When trials comparing it with other healthy diets were pooled, no clear difference in blood sugar control was found, although some individual trials did report one. No trial found for this page measured heart attacks, strokes, diabetes or death. Studies that score how closely people's ordinary eating resembles the pattern link higher scores with lower death rates, but those studies cannot show cause, and very few of the people in them were following the diet.

Is it safe? For most healthy adults the foods themselves are ordinary foods. Two cautions come up most. Leaving out dairy and iodized salt can leave a person short of calcium and iodine: in the 2-year trial, iodine levels in the urine of the women eating this way fell by about half within 6 months. And the American Heart Association placed it among the patterns least aligned with its heart-health guidance, because it excludes whole grains and legumes and can be high in saturated fat when it leans on fatty meat.

Who should not do it without talking to a doctor or dietitian first? Anyone who is pregnant, breastfeeding or planning a pregnancy. Anyone with low bone density or a thyroid condition. Anyone with kidney disease. Anyone taking insulin, a sulfonylurea, blood pressure medication or warfarin. Anyone with a history of disordered eating. And parents thinking of feeding a child this way.

Related pages: Mediterranean Diet and Ketogenic Diet. Also related: Low-Carbohydrate Diets, Carnivore Diet, Whole30 and Autoimmune Protocol Diet. Full list on the archive index.

1. Overview

What you eat

The core foods are meat, poultry, fish and shellfish, eggs, vegetables, fruit, nuts and seeds. The organization founded by Loren Cordain, author of the book The Paleo Diet, describes it as plenty of vegetables and fruits, natural meats and seafood, and some nuts and seeds, and says that by volume the diet is primarily plant-based (The Paleo Diet Team, n.d.-a, n.d.-b). Harvard's Nutrition Source lists fresh lean meats, fish, shellfish, eggs, nuts, seeds, fruits, vegetables, olive oil, coconut oil and small amounts of honey, with some root vegetables, such as sweet potatoes and cassava, allowed in moderation in some versions (Harvard T.H. Chan School of Public Health, n.d.).

The diet sets no calorie target and no fixed ratio of protein, fat and carbohydrate. Its promoters say this is deliberate: hunter-gatherers near the equator ate more carbohydrate and those farther north ate more protein and fat, so the diet is defined by food groups rather than by numbers (The Paleo Diet Team, n.d.-a). In practice, leaving out grains and legumes usually makes it higher in protein and lower in carbohydrate than a typical Western diet, which the founder's organization also says (The Paleo Diet Team, n.d.-a).

What you avoid or limit

The founder's organization names the biggest categories to avoid as dairy foods, grains, legumes and processed foods, and adds added sugar and salt (The Paleo Diet Team, n.d.-b). Grains here means all of them, whole or refined: wheat, rice, oats, corn and the rest. Legumes means beans, lentils, peas, peanuts and soy. The Nutrition Source's summary also lists refined vegetable oils, such as canola, among foods not allowed, and notes that white potatoes are usually avoided because of their high glycemic index (Harvard T.H. Chan School of Public Health, n.d.).

How strict the rules are depends on whose version a client is following. The founder's organization does not ask newcomers to eat this way all the time. It promotes an 85/15 principle, in which about 15 percent of meals can be anything, and says people can eat 50 to 85 percent of their meals this way and still benefit (McNew, n.d.; The Paleo Diet Team, n.d.-b). Other versions treat the exclusions as firm rules. Coffee is a good example of how versions differ: the founder's organization now allows it, while the Nutrition Source lists it among foods not allowed (Harvard T.H. Chan School of Public Health, n.d.; The Paleo Diet Team, n.d.-b).

Where it came from

The idea came from medicine and anthropology before it became a popular diet. In 1985 S. Boyd Eaton and Melvin Konner first published what they later called the evolutionary discordance hypothesis: that departures from the eating and activity patterns of hunter-gatherer ancestors contribute to the chronic diseases of modern societies (Konner & Eaton, 2010). In 2005 Loren Cordain and colleagues, Eaton among them, argued that foods and food processing introduced since farming began, about 10,000 years ago, changed 7 features of the human diet: its glycemic load, the types of fat in it, its balance of protein, fat and carbohydrate, its density of vitamins and minerals, its acid-base balance, its ratio of sodium to potassium, and its fiber content (Cordain et al., 2005).

Cordain's book, The Paleo Diet, was published in 2002 and turned the idea into a popular plan. After he retired in 2019, the company he founded, also called The Paleo Diet, continued under new leadership and added food certification and brand licensing programs (The Paleo Diet Team, 2022). The name took off far beyond that company. A 2015 systematic review notes that "Paleo" was the most searched diet-related term on Google in 2014 (Manheimer et al., 2015).

What it claims to do

The central claim is evolutionary. The founder's organization calls it "the diet to which the human species is best adapted" and says that eating it means eating the foods the body is genetically programmed for. It argues that most foods in the modern Western diet arrived too recently for the human body to have evolved to digest them properly (The Paleo Diet Team, n.d.-a). On that basis it claims wide benefits: that the diet reduces inflammation, strengthens immunity, and helps fight type 2 diabetes and autoimmune disorders, and that very few chronic illnesses fail to respond to it (The Paleo Diet, n.d.; The Paleo Diet Team, n.d.-a). Its home page also promises clear skin, better sleep, mental clarity, better endurance and improved recovery (The Paleo Diet, n.d.).

It makes narrower claims about particular foods as well: that grains carry substances it calls anti-nutrients, such as lectins and saponins, that open the lining of the gut and, over time, lead to inflammatory and autoimmune diseases and cancer (The Paleo Diet Team, n.d.-a). These are the promoter's claims, reported as claims. Section 4 sets out what trials have and have not tested, and section 6 takes the myths one at a time. The difference matters, because the evolutionary premise is a hypothesis about the past, while the trials test a modern diet in modern people.

What it gets right

The foods it puts at the center, vegetables, fruit, nuts, fish and eggs, are foods heart-health guidance also asks for, and it cuts out sugary drinks, sweets, refined grains and heavily processed food. The American Heart Association, while rating the pattern poorly overall, names its strengths as an emphasis on nonstarchy vegetables, nuts and fish and minimal intake of foods and drinks with added sugar (Gardner et al., 2023). The Nutrition Source makes the same point: the diet includes nutrient-dense whole fresh foods and steers people away from highly processed foods with added salt, sugar and unhealthy fats (Harvard T.H. Chan School of Public Health, n.d.).

That overlap is what lets a coach honor a client's reasons without endorsing the whole package. A client who has started eating more vegetables, cooking at home and drinking less soda has made changes that most dietary guidance supports. Where the diet parts company with guidance is in what it leaves out, and section 6 covers that.

How clients describe it, and what it gets confused with

Clients say "I'm eating paleo," "I eat like a caveman," "I cut out grains and dairy," "I'm grain-free," or "I'm on the Stone Age diet." The diet has also been called the hunter-gatherer diet and the caveman diet (Jones, 2026). A client may also mean the 85/15 version, a strict version, or a set of recipes from a gym or a social media account, so it is worth asking what it looks like on their plate.

It is most often confused with low-carbohydrate diets and the Ketogenic Diet, because cutting grains lowers carbohydrate; with the Carnivore Diet, an all-animal-food pattern; with Whole30, a commercial program; and with the Autoimmune Protocol Diet, an elimination diet. The boundary with the family page, Low-Carbohydrate Diets, is this: paleo is defined by which food groups it leaves out rather than by a carbohydrate target, so a paleo menu heavy in fruit and root vegetables may not be low in carbohydrate at all, while a low-carbohydrate diet that keeps cheese and cream is not paleo.

2. In practice

A typical day of eating

Breakfast is scrambled eggs with spinach and mushrooms cooked in olive oil, with a bowl of berries. Lunch is a large salad with grilled chicken, avocado, cucumber, tomatoes and sunflower seeds, dressed with olive oil and lemon. A snack is an apple with a handful of almonds. Dinner is baked salmon with a roasted sweet potato and broccoli. Water is the usual drink, with coffee or tea in the versions that allow them. Nothing here is unusual food. What stands out is what is missing: no bread, cereal, rice, pasta, milk, yogurt, cheese, beans or lentils.

Cost, products, and who profits

No membership or product is required. Food costs depend on the version and the foods it replaces. A modeling study used U.S. Department of Agriculture data and the department's Thrifty Food Plan, a model for eating well on a limited food budget, with 2001 to 2002 U.S. food prices for a woman aged 20 to 50. Within the plan's budget it found a paleo menu that met most nutrient targets but fell short on calcium, fiber and iron; a 9.3 percent higher modeled food budget was needed to meet the modeled nutrient constraints except calcium, which remained below its target (Metzgar et al., 2011). It is a model of what such a diet could cost, not a measure of what people following paleo spend.

In a 4-week Australian trial in 39 healthy women, more of the paleo group than the comparison group said their grocery shopping had become more expensive: 11 of 21, against 1 of 16, in the paper's questionnaire table; the abstract gives the paleo figure as 69 percent (Genoni, Lo, et al., 2016). The Nutrition Source lists higher cost among the diet's pitfalls, along with the time it takes to plan and cook meals from fresh food (Harvard T.H. Chan School of Public Health, n.d.).

Money attaches to the name in several places. The company founded by Loren Cordain sells books, meal plans and guides, and runs 2 food certification programs, TRUEPALEO and PaleoFLEX, along with a brand licensing program for food makers (The Paleo Diet Team, 2022). U.S. News & World Report notes that more meal delivery services and packaged foods labeled "paleo-friendly" have become available, and that dietitians warn many of them are highly processed (Jones, 2026). A client who has been buying paleo-labeled snack bars, baking mixes and supplements may be paying more for products that sit outside the diet's own principles.

For someone with little money, time or store access, the expensive parts are fresh meat and fish. Frozen vegetables, canned fish, eggs and seasonal produce are cheaper ways to eat within the pattern, and the founder's organization itself suggests eating paleo for only part of the week (McNew, n.d.).

Environmental footprint

Because the diet removes plant proteins and leans on meat and fish, its footprint depends heavily on how much and what kind of meat a person eats. One study estimated the greenhouse gas emissions of diets as U.S. adults ate them, from national dietary recall data collected from 2005 to 2010. The 62 people whose diets fit the study's paleo-style definition had an average of 2.62 kilograms of carbon dioxide equivalents per 1,000 calories, compared with 2.23 for all other omnivorous diets, 1.16 for vegetarian diets and 0.69 for vegan diets; the vegan and vegetarian diets were significantly lower than the paleo-style diets (O'Malley et al., 2023).

Those figures are estimates built from what people reported eating, not measurements, and the paleo-style group was very small. Within the pattern, a person who eats more fish, eggs and poultry and less beef will have a smaller footprint than one who eats beef daily.

Cultural fit

The pattern fits most easily into food traditions built around meat or fish, vegetables and fruit. It conflicts with the many traditions built around a grain, a legume or a dairy food: rice in much of Asia, corn tortillas and beans in much of Latin America, lentils and flatbreads in South Asia, and milk and cheese in pastoral cultures. For a client from one of those traditions, following paleo strictly can mean giving up the staple foods of family meals and holidays. The flexible versions, which allow a share of meals outside the rules, are the usual way people adapt it, and keeping a traditional dish while eating more vegetables and less processed food keeps most of what the pattern gets right.

What makes people stop

Direct evidence comes mainly from the 2-year Swedish trial. Interviews with 12 women after it ended described an early "honeymoon phase" of weight loss and support, followed by an everyday-life phase and an "it's up to you" phase that held the largest obstacles; the home environment and support from family and friends decided whether the new habits lasted (Ahlgren et al., 2016). Those interviews covered both diets in the trial, not paleo alone. In the trial itself, fewer women left the paleo group than the comparison group, 8 against 13 over 2 years, although women in the paleo group never reached the high protein target they were given (Manheimer et al., 2015; Mellberg et al., 2014).

In the 4-week Australian trial, most women in both groups found their diet easy to follow once they had routines, but 9 of 21 in the paleo group were unsure or did not believe the diet fit their idea of healthy eating, against none in the comparison group, and more reported diarrhea (Genoni, Lo, et al., 2016). The American Heart Association names the restrictive nature of the pattern as a likely limit on long-term adherence (Gardner et al., 2023). Beyond those studies, what follows is observation rather than measured data: eating out, travel, family meals built around bread or rice, and the cost of fresh meat and fish are the usual pressure points.

What happens when you stop

The searches for this page found no study that followed people after they stopped eating this way. The closest evidence is what happened within the longest trial as time went on. In 70 women followed for 2 years, the paleo group lost more fat mass and more from the waist than the comparison group at 6 months, but by 24 months the difference in fat mass was no longer clear, and weight in the 2 groups had moved closer together; the larger fall in triglycerides was still there at 24 months (Mellberg et al., 2014). Most other trials lasted from 2 weeks to 6 months, too short to say which changes last.

Common variations

The founder's version, promoted by The Paleo Diet company, is the reference version, and its 85/15 principle makes it more flexible than many clients expect (McNew, n.d.). The modified Paleolithic diet developed by Terry Wahls for multiple sclerosis, known as the Wahls diet, removes gluten-containing grains, dairy and eggs and asks for large amounts of vegetables; it has been tested in small trials described in section 4 (Titcomb et al., 2020; Wahls et al., 2021). The Autoimmune Protocol Diet is a separate elimination diet. Paleo ketogenic diets combine the paleo food list with a very low carbohydrate intake; the founder's organization credits paleo with helping to spark them (The Paleo Diet Team, 2022). The trials themselves used their own versions, and section 4 says which version each tested.

3. For the coach

SCOPE OF PRACTICE

A health and wellness coach does not prescribe, adjust, endorse or discourage this or any way of eating, and does not diagnose or treat. The coach helps the client understand what they have chosen, notice how it is going, and decide what to do next. Several points belong to someone else. A client who wants to use this diet to manage diabetes, high blood pressure, a thyroid condition, kidney disease or an autoimmune condition needs the clinician who treats that condition, and usually a registered dietitian.

The diet's documented risks fall on particular groups rather than on healthy adults in general. For a client in any of these 8 groups, the coach's role includes making sure the client has medical oversight for the change:

• Pregnant, breastfeeding or planning a pregnancy: the obstetric clinician and a dietitian, because the diet removes the main food sources of calcium and iodine.
• Low bone density, a history of fractures or a high risk of osteoporosis: their clinician and a dietitian, for calcium and vitamin D.
• A thyroid condition: the clinician who treats it, because of the iodine finding.
• Kidney disease: the kidney care team, because protein and potassium needs depend on the stage of the disease, lab results and whether the person is on dialysis. The pattern's fruit and vegetables are not a hazard for everyone with kidney disease.
• Taking insulin, a sulfonylurea, blood pressure medication or warfarin: the client keeps the prescriber informed before making a substantial change in eating.
• High LDL cholesterol or heart disease, with a version heavy in fatty meat: their physician.
• A child: a parent who wants to feed a child this way involves the pediatric clinician and a dietitian.
• A history of disordered eating: the coach’s own referral process, or the client's clinician under an existing care plan.

A coach does not read or interpret lab results, such as cholesterol or thyroid tests.

Who does what

The physician

Decides whether the diet is medically safe for this person and orders and reads the tests that bear on it: a cholesterol panel, which can move in either direction depending on how much saturated fat the version contains; blood sugar measures in a person with diabetes; kidney function and potassium in a person with kidney disease or on medications that raise potassium; and thyroid tests where iodine intake is a concern. Adjusts any medication the change affects, particularly insulin, sulfonylureas and blood pressure medication.

The registered dietitian

Builds and monitors an individual eating plan. For this diet that usually means checking whether the version a client follows meets their needs for calcium, vitamin D, iodine and fiber, and finding replacements for what the excluded food groups supplied; adapting it to a diagnosed condition such as diabetes or kidney disease; and planning it for pregnancy, breastfeeding, childhood, older age or heavy training.

The health and wellness coach

Finds out what the client hopes the diet will do and where that hope came from. Explores how the version they chose fits their budget, their cooking time, the people they eat with and the foods of their culture. Helps the client choose the parts they want to keep, set a first step small enough to hold, and notice how it is going over months rather than weeks. With the client's permission, can share general information from recognized authorities, such as what a federal fact sheet says about calcium or iodine, and explore how the client wants to use it. Notices whether the eating is widening or narrowing, and holds the referral line when a question belongs to a clinician.

What a client bringing this diet needs

Clients bring paleo for different reasons: to lose weight, to manage blood sugar, to feel better after years of processed food, to follow a partner or a gym, or because the evolutionary story made sense to them. Some have already felt better and want to keep going; others feel pressure from a community that treats grains and dairy as harmful. The reason shapes the conversation.

What the coaching conversation offers that a search engine cannot is room to separate the parts of the diet the client values from the parts they took on as a package. Many clients who say "paleo" have mostly started cooking more and eating more vegetables. Others have built a long list of forbidden foods. The coach explores what this client means by it and what they want from it, and supports the client's own decisions within the referral boundaries below.

What to ask

• When you say you're eating paleo, what does a usual day look like for you?
• What were you hoping would change when you started, and what has changed so far?
• Which parts of it feel easy to keep, and which parts feel like work?

Referral red flags

A client taking insulin or a sulfonylurea who has cut grains, starchy foods and sweets, or who reports shakiness, sweating or confusion between meals, may be having low blood sugar. The episode is treated first under the client's own plan, with emergency help for severe symptoms or an episode they cannot manage, and telling the prescriber is the separate step that follows. A client on warfarin who is eating far more leafy greens than before should tell the prescriber, because people taking warfarin need a steady amount of vitamin K from day to day (National Institutes of Health Office of Dietary Supplements, 2021).

A client with kidney disease, or on blood pressure medication, who has sharply increased meat, fruit and vegetables is describing a change their care team needs to know about, because protein and potassium needs in kidney disease depend on stage, lab results and treatment, and some widely prescribed blood pressure medications raise blood potassium (Palmer & Clegg, 2016). The kidney care team decides; the pattern's fruit and vegetables are not a hazard for everyone with kidney disease.

A client who is pregnant or breastfeeding and has cut dairy and iodized salt belongs with the obstetric clinician and a dietitian. A client who reports a swelling at the front of the neck, which a federal fact sheet describes as often the first visible sign of iodine deficiency (National Institutes of Health Office of Dietary Supplements, 2024), a broken bone from a minor fall, new and lasting fatigue, or weight loss they did not intend is describing something a clinician needs to see, and the coach does not guess at the cause.

A client whose list of forbidden foods keeps growing, who feels anxious or guilty after eating bread or cheese, or who has stopped eating with family and friends is worth asking about it directly: what each rule is for, whether it causes distress, whether it is narrowing what they eat, and whether it is getting in the way of daily life. There are ordinary reasons for cutting a food, from an allergy or celiac disease to a dietitian's plan. Where the answers raise a real concern about disordered eating, the coach follows their own referral process.

Special populations

Pregnancy and breastfeeding

The search for this page found no trial of the diet in pregnancy. One small retrospective study in Israel compared 37 low-risk pregnant women who had eaten this way throughout pregnancy with 39 on a regular diet: glucose screening scores were lower and hemoglobin and iron stores higher in the paleo group, and babies weighed a little less, 3,098 grams against 3,275, with no clear difference detected in the newborn outcomes reported (Lavie et al., 2019). A study of that design cannot show what the diet caused. The bigger concern is iodine. Pregnant women need about 50 percent more iodine than other women, and the iodine in breast milk depends on how much the mother gets (National Institutes of Health Office of Dietary Supplements, 2024). This diet removes 2 of the largest sources, iodized salt and dairy foods (Manousou et al., 2018), although the seafood and eggs it keeps also supply iodine (National Institutes of Health Office of Dietary Supplements, 2024). Calcium needs stay at 1,000 milligrams a day for adult women during pregnancy and breastfeeding (National Institutes of Health Office of Dietary Supplements, 2023). Any plan to eat this way during pregnancy or breastfeeding belongs to the obstetric clinician and a dietitian.

Children and adolescents

The search for this page found no trial of the paleo diet in children or adolescents. Children and teens need 700 to 1,300 milligrams of calcium a day depending on age, more than adults at 9 to 18 years, and milk, yogurt and cheese are the main sources for most people in the United States (National Institutes of Health Office of Dietary Supplements, 2023). A child's eating belongs to the family and the pediatrician, and a coach works with the adult in front of them.

Older adults

Much of the trial evidence comes from adults around 60: the 2-year trial enrolled women with an average age of 60 after menopause, and the Swedish trial in heart disease had average ages of 57 and 65 in its 2 groups (Manheimer et al., 2015; Mellberg et al., 2014). In the 2-year trial the paleo group lost more lean mass in the first 6 months than the comparison group, 1.3 kilograms against 0.4 (Mellberg et al., 2014). Women over 50 and all adults over 70 need 1,200 milligrams of calcium a day, and the body absorbs and keeps less calcium after menopause (National Institutes of Health Office of Dietary Supplements, 2023). An older adult with low bone density or a history of fractures needs a clinician and a dietitian before cutting dairy.

Athletes and people with high activity

A 2021 review of trials noted a lack of experiments in professional athletes and called for longer studies to judge performance (Frączek et al., 2021). In a pilot trial in 14 male endurance athletes, both a paleo diet and a mixed diet, each with sprint interval training, improved running performance over 6 weeks, with no clear difference between them; the authors concluded the paleo diet cannot be recommended unreservedly for endurance athletes (Zdzieblik et al., 2024). In 25 professional handball players, body mass was lower after 8 weeks on a paleo diet and body composition did not change in either group (Pięta et al., 2023). In 20 young women followed for 8 weeks, the group given MyPlate advice with exercise improved aerobic fitness more than the group given paleo advice with exercise, though the authors caution that low compliance with the exercise advice may confound that result (Popp et al., 2018). A person training hard who has cut grains and starchy foods may not be eating enough carbohydrate or total food for their training, which is a question for a sports dietitian.

People taking medication for diabetes, blood pressure, or blood thinning

The diet's food changes can lower blood sugar, blood pressure and weight, which is why the prescriber needs to know. A client on insulin, a sulfonylurea or blood pressure medication who plans a substantial change in eating keeps the prescriber informed before making it. Some blood pressure medications raise blood potassium and can call for limits on potassium-rich foods (Palmer & Clegg, 2016). People taking warfarin need a steady vitamin K intake, and a sudden large increase in leafy greens can change how the drug works (National Institutes of Health Office of Dietary Supplements, 2021).

People with a history of disordered eating

The search for this page found no study of whether starting the diet raises the risk of disordered eating. In one cross-sectional study of 393 adults following different restrictive diets, the 42 people in the paleo group reported the lowest levels of eating disorder symptoms, food cravings and emotional eating of any group; they chose the diet themselves and were measured once, so the study cannot say whether the diet affects those symptoms (Norwood et al., 2019). The rules still matter for someone with this history. A diet built on lists of foods humans supposedly cannot digest can turn eating into a set of rules, and a concern goes to the client's clinician under the existing care plan.

Client misconceptions

Three come up most. The first is that humans are not adapted to grains, dairy or legumes because these foods arrived after the Stone Age. That is the diet's founding hypothesis, not an established finding, and it does not account for how much human diets varied across climates and regions before farming.

The second is that paleo has been shown to prevent heart disease or diabetes. The trials measured risk factors such as waist size, triglycerides and blood sugar for weeks to months, and the searches for this page found no trial that measured heart attacks, diabetes or death. The third is that paleo means eating a lot of meat. The founder's organization says the diet is mostly plants by volume, while the American Heart Association describes the pattern as tending to be high in saturated fat; which one a client is eating depends on their version. Each is addressed in section 6.

🤝 COACHING CONNECTION

Rachel started eating paleo with her husband after their gym ran a challenge, and she comes in pleased: she has been cooking most nights and has stopped the afternoon vending-machine habit. She mentions she has dropped milk and yogurt and wonders whether that matters, because her mother broke a hip last year. The coach asks what she likes about how she is eating now. Rachel says the cooking with her husband. The coach asks what she knows about her own bone health. She says she has never asked. The coach asks what she would want to find out, and from whom. Rachel decides to ask her doctor about a bone density test at her next visit and to ask whether a dietitian could look at her calcium. She keeps the cooking. Nothing was recommended, and the diet was not judged.

4. The evidence

(select the heading to open or close this section)

The evidence comes in 2 kinds that have to be kept apart. Trials of the diet are small and short, usually a few dozen people followed for 2 weeks to 6 months, and most were done in people who already had weight, blood sugar or heart problems. Against diets based on national healthy eating guidance, they found somewhat larger short-term improvements in waist size and triglycerides, with smaller and less certain differences in blood pressure and cholesterol, and when trials against other healthy diets were pooled, they did not find a clear difference in blood sugar control, although some individual trials did. Cohort studies, which score how closely people's ordinary eating resembles the pattern, link higher scores with lower death rates, but they cannot show cause. No trial found for this page measured heart attacks, strokes, new diabetes, cancer or death.

The evolutionary premise is a separate matter from all of this. Section 1 describes what the diet's originators say it is based on. The trials below do not test that premise; they test whether a modern diet that removes grains, dairy foods and legumes changes risk factors in modern people, and each one tested its own version against its own comparison diet.

Evidence from randomized controlled trials

A trial assigns people to a diet by chance and compares them with people assigned to something else, which is the strongest way to test whether the diet itself causes a result. None of the paleo trials could hide from participants which diet they were eating, which matters most for outcomes people report themselves. The trials differ in 3 ways worth knowing before reading their results.

First, most gave advice rather than food. In the Swedish trials, people were taught the diet and ate as much as they liked; the longest of them, in women after menopause, set targets of 30 percent of calories from protein, 40 percent from fat and 30 percent from carbohydrate, with lean meat, fish, eggs, vegetables, fruit, berries and nuts, and no dairy, cereals, added salt, or refined fats and sugar (Mellberg et al., 2014). Two trials supplied the food: a 2-week Dutch trial delivered meals designed to keep weight stable, and a 2-week United States trial in type 2 diabetes ran a metabolically controlled diet (Boers et al., 2014; Masharani et al., 2015).

Second, in the metabolic trials the comparison diets were healthy diets, not typical Western eating. Other studies used usual diet as the comparison or tested exercise added to a paleo diet (Irish et al., 2017; Lee et al., 2021; Otten et al., 2017). The healthy comparison diets included a Mediterranean-like diet with whole grains and low-fat dairy foods, a diabetes diet following guidelines, the Nordic Nutrition Recommendations, the Dutch Health Council's guidelines and the Australian Guide to Healthy Eating (Genoni, Lyons-Wall, et al., 2016; Manheimer et al., 2015). A paleo diet that does better than one of these has done better than a healthy diet, not than fast food. Third, in several trials the paleo group ate less and lost more weight, which makes it hard to tell the effect of the foods from the effect of the weight loss. Section 5 returns to that question.

Cardiometabolic outcomes

The most carefully rated evidence is a 2015 systematic review of 4 randomized trials with 159 participants who had at least one feature of the metabolic syndrome, the cluster of large waist, high triglycerides, low HDL cholesterol, high blood pressure and high fasting blood sugar. It used results from the first measurement in each trial, at up to 6 months. Compared with guideline-based diets, the paleo diets lowered waist circumference by 2.38 cm more, from 0.04 to 4.73 cm more, and triglycerides by 0.40 mmol/L more, from 0.04 to 0.76 more (Manheimer et al., 2015).

In the same review, systolic blood pressure was 3.64 mm Hg lower, from 7.36 lower to 0.08 higher, and diastolic pressure 2.48 mm Hg lower, from 4.98 lower to 0.02 higher; both intervals just reach no difference. HDL cholesterol and fasting blood sugar did not differ clearly. The reviewers rated each of these outcomes moderate in certainty using GRADE, lowering each by 1 level for imprecision or, for triglycerides, inconsistency (Manheimer et al., 2015). None of the 4 trials measured quality of life, and only 1 reported on adverse events.

A 2019 review pooled 8 eligible reports of trials, one of them a substudy of another included trial that was used only for an outcome the main report lacked, and found lower body weight, waist circumference, blood pressure, total cholesterol, triglycerides, LDL cholesterol and C-reactive protein, a blood marker of inflammation, with paleo diets (Ghaedi et al., 2019, 2020).

That review has a history a reader should know. After publication, statisticians reported effect sizes and confidence intervals they could not reproduce, unexplained choices about which results were used, and mislabeled units. The authors reanalyzed the data, and the journal retracted the original article and republished a corrected version (Chen et al., 2020; Ghaedi et al., 2020; "Effects of a Paleolithic Diet," 2020). This page cites the corrected version. Its own sensitivity analyses showed that the results for blood lipids, systolic blood pressure and C-reactive protein changed when single trials were removed, and the authors concluded that the evidence is not conclusive (Ghaedi et al., 2019).

Two newer reviews reported in the same direction. A 2022 review that included 10 articles on adults with metabolic disorders reported lower insulin resistance, cholesterol, triglycerides, blood pressure and C-reactive protein with paleo diets (Sohouli et al., 2022). The 2022 review's full text was closed to this page, so its study tables and exact units were not checked; this page reports only what its abstract states. A newer review also reported favorable pooled results, but its included-study list contains multiple reports from the same trial and a diet-choice study classified as randomized. Its certainty descriptions also contain inconsistencies, so this page does not use that review to determine its ratings (Bahrami et al., 2026).

Two network analyses, which compare many diets at once by linking trials that share a comparison, placed paleo diets alongside other healthy patterns. In people with high or high-normal blood pressure, DASH ranked first for lowering blood pressure and the paleo diet second, but the credibility of most comparisons was rated very low to moderate (Schwingshackl et al., 2019). In people with type 2 diabetes, the paleo diet ranked third for lowering HbA1c, a measure of average blood sugar, behind low-carbohydrate and Mediterranean diets, and the authors cautioned that only 1 paleo trial was available (Schwingshackl et al., 2018).

LDL cholesterol

LDL cholesterol deserves its own look, because a common worry about this diet is that more meat means more saturated fat and higher LDL. The older pooled trials did not show an average LDL increase. In the 2019 review, LDL was 0.13 mmol/L lower with paleo diets across 5 trials, from 0.26 to 0.01 lower, an interval that comes close to no difference; removing any one of 3 trials made the result statistically uncertain, and one test suggested that small studies with unfavorable results may be missing, although a correction for that changed the estimate little (Ghaedi et al., 2019).

In the 2-year trial, LDL fell in both groups and the paleo diet did not demonstrate a different change from the Nordic diet over 24 months (Mellberg et al., 2014). In the 4-week Australian trial, LDL fell within the paleo group, and the difference from the comparison group, 0.11 mmol/L lower, from 0.3 lower to 0.1 higher, was not clear (Genoni, Lyons-Wall, et al., 2016). An American study reported lower LDL after 4 months of paleo eating than after 4 months of a heart-healthy diet, but the same 20 people followed the 2 diets in a fixed order rather than a random one, so the result could reflect time or practice as much as the diet (Pastore et al., 2015).

The important limit is which version was tested. The trial diets in the 2019 review were built on lean meat, fish and unsaturated fats: in the 2-year trial, saturated fat fell as a share of calories in the paleo group while monounsaturated and polyunsaturated fats rose (Mellberg et al., 2014). The American Heart Association, describing the pattern as it is popularly followed, says it emphasizes meat, poultry and fish and tends to be high in saturated fat as a result (Gardner et al., 2023).

A later 8-week study in 25 male handball players tested a paleo diet the authors described as high in saturated fat and found no clear LDL difference. Its small size, short duration and athletic population cannot establish long-term lipid safety or the effects of other high-saturated-fat versions, such as one built on fatty meat, bacon or coconut oil (Pięta et al., 2023). That question belongs with the client's clinician and a lipid test.

Blood sugar and diabetes

The early trials that brought the diet attention were in blood sugar. In 29 men with heart disease and either impaired glucose tolerance or type 2 diabetes, 12 weeks of paleo advice lowered the blood sugar response to a glucose drink by 26 percent, against 7 percent on a Mediterranean-like diet, a difference that did not depend on the change in waist size (Lindeberg et al., 2007). In 13 people with type 2 diabetes who ate each diet for 3 months in random order, HbA1c was 0.4 percentage points lower after the paleo period than after a diabetes diet, along with lower triglycerides, diastolic blood pressure, weight and waist size and higher HDL cholesterol (Jönsson et al., 2009).

Pooled, the picture is less clear. A 2020 review of 4 trials with 98 people with impaired glucose metabolism compared paleo diets with Mediterranean, diabetes and Dutch guideline diets, and no clear difference was detected in fasting glucose, fasting insulin, insulin resistance, HbA1c or the response to a glucose drink (Jamka et al., 2020).

A 2025 trial in 14 people with type 2 diabetes kept body weight stable and matched the 2 diets for protein, fat, carbohydrate and glycemic load, so that the main difference was whether grains, dairy foods and legumes were eaten; fiber differed between them, and the trial did not demonstrate a clear difference in HbA1c over 4 weeks (Fontes-Villalba et al., 2025). Trials in which every participant ate the paleo diet, with or without supervised exercise, report large within-group falls in HbA1c, but without a non-paleo comparison group they cannot show that the diet caused them (Otten et al., 2017).

Cancer

The searches for this page found no randomized trial of the paleo diet that measured cancer, either new cancers or cancer outcomes. The trials reviewed here measured risk factors over weeks to months and cannot establish any effect on cancer. Section 4's cohort studies describe associations with cancer.

Body weight, as measured

This archive reports body weight as something a study measured, in that study's own numbers, and not as a goal or as a measure of whether a diet worked; see the standing rule in the review record at the foot of this page. The one exception is weight a person loses without meaning to, which can signal a health problem and is a reason to involve a clinician, never a sign that a diet worked.

In the 2015 review, body weight fell 2.69 kg more on the paleo diets than on the guideline-based diets at up to 6 months, from 0.52 to 4.87 kg more, rated moderate in certainty (Manheimer et al., 2015). The corrected 2019 review reported 1.68 kg more, pooled from 6 trials (Ghaedi et al., 2019). In the 2-year trial, the paleo group lost more weight at 6 and 12 months; at 12 months the averages were 8.7 kg and 4.4 kg, and at 24 months the difference between the groups was no longer statistically clear (Mellberg et al., 2014). In that trial the paleo group also lost more lean mass in the first 6 months, 1.3 kg against 0.4 kg. Both groups in that trial reported eating fewer calories than at the start, without being asked to.

Mortality

The searches for this page found no randomized trial of the paleo diet that measured death, from any cause or from a specific cause. The trials were too small and too short to do so, and none of them establishes an effect on survival. The cohort studies below describe associations with death rates in people whose ordinary eating scored closer to the pattern.

Eating behavior and wellbeing

None of the 4 trials in the 2015 review measured quality of life (Manheimer et al., 2015). The searches for this page found trials that measured fatigue and quality of life only in multiple sclerosis, using the Wahls version of the diet. In a partly randomized controlled pilot in relapsing-remitting multiple sclerosis, 34 people were allocated to the Wahls diet or to their usual diet, 19 completed follow-up and 17 were in the primary per-protocol analysis, which left out 2 diet-group participants who did not keep to the diet; fatigue and quality of life improved more in the diet group (Irish et al., 2017). Although the abstract calls it randomized, the methods say later participants were assigned by fatigue score rather than by chance.

In a larger trial, 87 people were randomly assigned to the Wahls diet or to the Swank diet, a low-saturated-fat diet; both groups reported improvements in fatigue and physical quality of life within their own group over 12 and 24 weeks, and the trial had no usual-diet group to show how much of that came from the diets themselves (Wahls et al., 2021). People with multiple sclerosis who want to try either diet need their neurologist and a dietitian; section 3 covers the referral.

A smaller 12-week pilot randomly assigned 15 people with multiple sclerosis, most with a progressive form, to a modified paleo diet, a modified ketogenic diet or their usual diet. The modified paleo diet allowed legumes and limited gluten-free grains, unlike the strict reference version. Fatigue improved within the modified paleo group, but the trial did not demonstrate a clear difference between groups in fatigue or quality of life at 12 weeks, and a change within one group does not show that one diet works better than another (Lee et al., 2021).

In the 4-week Australian trial, the paleo group reported more diarrhea than the comparison group, and more of them doubted that the diet was healthy (Genoni, Lo, et al., 2016). A cross-sectional study of people already following different diets, described in section 3, found low levels of eating disorder symptoms among the paleo group, a finding that cannot speak to cause (Norwood et al., 2019).

Evidence from long-term prospective cohort studies

A cohort study follows people who already eat a certain way and records what happens to them. It can show that a pattern goes with an outcome; it cannot by itself show that the pattern caused it. In this literature, researchers build a score from a food questionnaire that gives points for eating more of the foods the diet favors and fewer of the foods it excludes, and then compare people with the highest and lowest scores. Very few people in these cohorts were following a paleo diet. In a Swedish cohort, for example, the median share of food drawn from paleo food groups was 40 percent (Rydhög et al., 2024). The comparison is between ordinary diets that lean more or less toward the pattern, and the scores differ from study to study.

Cardiometabolic outcomes

In 24,104 adults in the Malmö Diet and Cancer Study in Sweden, followed for a median of 18 years, a higher share of food from paleo food groups went with fewer coronary events; the hazard ratio comparing the theoretical extremes of 0 and 100 percent was 0.61, from 0.43 to 0.86, and the association with type 2 diabetes was not clear, 0.82, from 0.61 to 1.10 (Rydhög et al., 2024).

In 18,210 Spanish university graduates followed for 12.2 years, with 165 cardiovascular events, the highest fifth of a paleo score had a hazard ratio of 0.45, from 0.27 to 0.76, against the lowest. The association weakened and was no longer statistically clear when the score's item for eating few ultra-processed foods was removed, and it appeared mainly in people who also ate in a Mediterranean way (de la O et al., 2022). That finding suggests the association may owe more to avoiding ultra-processed food than to avoiding grains, dairy foods or legumes.

Cancer

In 74,721 people in a United States cancer screening trial cohort, followed for an average of 9.2 years with 694 colorectal cancers, the highest quarter of a paleo score had a hazard ratio of 0.76, from 0.61 to 0.95, against the lowest. The association appeared in people with a body mass index under 30 and not in those at 30 or above (Xiao et al., 2023). In a biracial United States cohort described under mortality, the highest fifth of a paleo score had a hazard ratio for death from cancer of 0.72, from 0.55 to 0.95 (Whalen et al., 2017).

Body weight, as measured

In an online survey of more than 9,000 people who identified as followers of popular diets, those who had followed paleo for 1 to 5 years reported a lower body mass index than people who said they simply tried to eat healthy; participants were 82 percent female and 93 percent White, and recruited through diet communities (Karlsen et al., 2020). A survey of self-selected followers that relies on self-reported weight cannot show what the diet did.

Mortality

In 21,423 Black and White adults aged 45 and older in the REGARDS study, followed for a median of 6.25 years with 2,513 deaths, the highest fifth of a paleo score had a hazard ratio for death from any cause of 0.77, from 0.67 to 0.89, against the lowest; for death from cardiovascular disease it was 0.78, from 0.61 to 1.00. A Mediterranean score in the same people showed associations at least as strong, 0.63 for death from any cause (Whalen et al., 2017). The paleo score gave points for fruit and vegetable variety and for calcium from sources other than dairy, so it rewarded features shared with most healthy patterns.

In the Swedish cohort, with 10,092 deaths over a median of 18 years, the hazard ratio for death from any cause comparing 0 and 100 percent of food from paleo food groups was 0.55, from 0.45 to 0.66 (Rydhög et al., 2024). Because almost no one in that cohort ate 100 percent paleo foods, that figure is an extrapolation of the trend, not a comparison between real groups.

Highlighted studies

These 4 studies carry the most weight for this page: a review of trials with a published GRADE rating, the longest trial, a small crossover trial in type 2 diabetes, and a large cohort. Each is described so a reader can judge it without opening the paper.

On a narrow screen, scroll the table sideways to see every column.

Highlighted studies for the Paleo Diet

Study	Design	Sample size	Duration	Finding	The limitation that matters
Manheimer et al., 2015, a systematic review of paleo diets for the metabolic syndrome	Systematic review and meta-analysis of randomized trials, rated with GRADE	4 trials, 159 people with at least one feature of the metabolic syndrome	2 weeks to 6 months at the time point used	Against guideline-based diets, waist circumference 2.38 cm lower and triglycerides 0.40 mmol/L lower; blood pressure, HDL cholesterol and fasting blood sugar did not differ clearly. Each outcome rated moderate in certainty	Only 4 small trials, 3 of them from Sweden, all short, and none measured quality of life or disease
Mellberg et al., 2014, the 2-year Swedish trial	Randomized trial, ad libitum paleo diet against the Nordic Nutrition Recommendations	70 women after menopause with obesity; 49 completed	2 years	More fat loss and waist loss with paleo at 6 months, not clearly different at 24 months; triglycerides fell more with paleo at 6 and 24 months; LDL fell in both groups without a clear difference	30 percent of women were lost to follow-up, the paleo group never reached its protein target, and the women were one narrow group
Jönsson et al., 2009, a crossover trial in type 2 diabetes	Randomized crossover trial, paleo diet against a diabetes diet	13 adults with type 2 diabetes	2 periods of 3 months	After the paleo period, HbA1c was 0.4 percentage points lower, with lower triglycerides, diastolic blood pressure, weight and waist and higher HDL cholesterol	Very small, with no break between the 2 diet periods, and the paleo period also brought lower calorie intake and weight
Whalen et al., 2017, the REGARDS cohort	Prospective cohort study	21,423 Black and White adults aged 45 and older; 2,513 deaths	Median 6.25 years	Highest against lowest fifth of a paleo score: hazard ratio for death from any cause 0.77, from 0.67 to 0.89	Observational: it scores how closely ordinary eating resembles the pattern, few if any people were following the diet, and a Mediterranean score did at least as well

Head to head

Several metabolic trials compared paleo diets with another healthy eating pattern. Other studies used usual diet as the comparison or tested exercise added to a paleo diet. Against a Mediterranean-like diet with whole grains and low-fat dairy foods, 12 weeks of paleo advice improved the blood sugar response to a glucose drink more in men with heart disease (Lindeberg et al., 2007); the Mediterranean Diet page carries that pattern's own trials. Against diabetes diets, paleo improved HbA1c in one small crossover trial, but a weight-stable trial designed to isolate the food groups did not demonstrate a clear difference in HbA1c over 4 weeks (Fontes-Villalba et al., 2025; Jönsson et al., 2009). Against the Nordic Nutrition Recommendations over 2 years, it produced faster early fat loss and a lasting triglyceride difference, with most other differences fading (Mellberg et al., 2014).

Against the Australian Guide to Healthy Eating over 4 weeks, it produced more weight and waist loss and no clear difference in blood fats, blood sugar or C-reactive protein (Genoni, Lyons-Wall, et al., 2016). Against MyPlate advice in young women, with exercise, it produced smaller gains in aerobic fitness (Popp et al., 2018). Against the Swank diet in multiple sclerosis, both groups improved within themselves (Wahls et al., 2021). A small 12-week pilot in 15 people with multiple sclerosis directly compared modified paleo, modified ketogenic and usual diets. It did not demonstrate a clear difference between groups in fatigue or quality of life at 12 weeks (Lee et al., 2021).

Where the evidence is absent

The searches for this page found no randomized trial of the paleo diet that measured heart attacks, strokes, new cases of diabetes, cancer, fractures or death, and no trial that followed people for longer than 2 years. The trials it found were small, from 13 to about 90 people, and many came from a few research groups in Sweden. Most enrolled middle-aged or older adults with obesity, type 2 diabetes, heart disease or features of the metabolic syndrome, so they say little about healthy younger adults.

The searches found no trial in children, adolescents or pregnancy. Bone health was not measured in a way that can answer the calcium question: no trial found here measured fractures, and most trials that tracked calcium did so through intake or urine. A small 8-week study in athletes measured bone density and mineral content without detecting clear changes; it does not resolve long-term fracture or calcium adequacy questions (Pięta et al., 2023). The evolutionary premise itself is not something a diet trial can test. And the cohort studies measured resemblance to the pattern in people eating ordinary diets, not the diet as its promoters describe it.

5. Mechanisms

(optional reading; select the heading to open or close this section)

This section explains how the diet is thought to work in the body. You can skip it. Nothing in the coaching sections depends on it.

Established mechanisms

The clearest explanation for the trial results is that people ate less. In the 2-year trial, both groups reported eating fewer calories without being asked to, about 20 percent fewer in the paleo group at 24 months and 12 percent fewer in the comparison group, and the larger early weight and waist loss in the paleo group followed (Mellberg et al., 2014). Losing weight lowers triglycerides and waist size in most people, whatever the diet. Removing sugary drinks, sweets, refined grains and processed snacks, which the pattern does, also removes many easy calories.

Trials that tried to separate the food groups from weight loss give mixed answers. In a 2-week Dutch trial that tried to keep weight stable, blood pressure, triglycerides and cholesterol still improved more on the paleo diet, although weight fell a little more in that group despite the effort (Boers et al., 2014). In a 2025 trial that kept weight stable and matched the 2 diets for protein, fat, carbohydrate and glycemic load, though not for fiber, removing grains, dairy foods and legumes did not demonstrate a clear difference in HbA1c over 4 weeks (Fontes-Villalba et al., 2025). This small, short trial did not establish an extra glycemic benefit from excluding these food groups when weight and the matched dietary features were held similar.

Proposed mechanisms

Several further explanations are proposed, and none of them supports a claim in section 4. The first is the evolutionary discordance hypothesis itself: that the human body is better suited to pre-farming foods. Its own authors described it as a source of testable hypotheses that had to be checked by ordinary clinical and laboratory studies (Konner & Eaton, 2010). The second is the list of 7 nutritional changes since farming that Cordain and colleagues proposed, including higher glycemic load, a higher ratio of sodium to potassium, a more acid-forming diet and less fiber (Cordain et al., 2005); each is plausible, and each is shared with other healthy patterns that keep whole grains and legumes.

The third is the promoter's claim that compounds in grains and legumes, such as lectins, damage the gut lining and drive inflammation and autoimmune disease (The Paleo Diet Team, n.d.-a). The paleo-diet trials reviewed here did not isolate whether lectins in grains or legumes cause chronic disease. The fourth runs the other way and is a concern rather than a benefit. In a cross-sectional study, 44 long-term paleo followers ate less resistant starch, a type of fiber found in whole grains and legumes, than controls, had different gut bacteria, and in the strictest followers had higher blood levels of TMAO, a compound produced with the help of gut bacteria that has been associated with cardiovascular disease; TMAO was inversely associated with whole grain intake (Genoni et al., 2020). A study of that design cannot show that the diet caused those differences.

6. Risks, contraindications and myths

(select the heading to open or close this section)

Warnings from professional or regulatory bodies

None of the sources opened for this page reports a warning from a regulatory agency about the paleo diet, and no regulatory database was searched for one. The American Heart Association's 2023 scientific statement on popular diets scored 10 patterns against its dietary guidance and placed the paleo diet, with very low-carbohydrate and ketogenic diets, in its lowest tier, which it describes as "patterns of strong concern." Its reasons are that these patterns restrict food groups it considers essential to a heart-healthy diet, legumes and whole grains, and allow sources of saturated fat it strongly discourages, from meat in the case of paleo. It also gave the paleo pattern no points for oils because the pattern avoids the vegetable oils it recommends, and noted that the restrictions may lead to nutritional deficiencies (Gardner et al., 2023).

The Association's 2026 dietary guidance, the archive's source for nutrition claims, lists among the features of a heart-healthy pattern choosing foods made mostly with whole grains rather than refined grains, and shifting protein from meat toward legumes and nuts (Lichtenstein et al., 2026). The paleo diet agrees with that guidance on vegetables, fruit, nuts, fish, minimally processed food and added sugar, and departs from it on whole grains and legumes. The same 2023 statement suggested that clinicians counsel people following paleo to eat plenty of vegetables, fruits and nuts and to avoid overconsuming fatty meats and sodium (Gardner et al., 2023).

Nutrient gaps

Calcium is the gap seen most consistently. In the 4-week Australian trial, the paleo group ate 292 mg a day less calcium than the comparison group, from 99 to 486 mg less (Genoni, Lyons-Wall, et al., 2016). In the Dutch trial, the designed paleo menus supplied 575 mg a day against 1,181 mg in the comparison diet, and the authors argued that lower calcium loss in urine made up for it over 2 weeks (Boers et al., 2014).

Adults need 1,000 to 1,200 mg a day depending on age and sex, and milk, yogurt and cheese are the main sources for most people in the United States; people who do not eat dairy foods have to find calcium in canned fish with bones, certain vegetables such as kale and broccoli, fortified foods or supplements (National Institutes of Health Office of Dietary Supplements, 2023). The Nutrition Source notes that a person would need 5 or more servings of well-absorbed greens or bone-in fish a day to meet calcium needs from those foods alone (Harvard T.H. Chan School of Public Health, n.d.).

Iodine is the gap most likely to be missed. Table salt and dairy foods are 2 of the largest iodine sources, and the diet excludes both. In the 2-year trial, median urinary iodine in the paleo group fell from 71 to 36 micrograms per liter within 6 months while it stayed level in the comparison group, and the authors suggested considering iodine supplementation on this diet (Manousou et al., 2018). The Australian trial found 47.9 micrograms a day less iodine intake in the paleo group (Genoni, Lyons-Wall, et al., 2016).

Fiber depends on the version. The 2-year trial found no clear difference in fiber intake between the diets, and the Australian trial found fiber maintained (Genoni, Lyons-Wall, et al., 2016; Mellberg et al., 2014), but long-term followers in a cross-sectional study ate less resistant starch, a kind of fiber concentrated in whole grains and legumes (Genoni et al., 2020). In people with multiple sclerosis following the Wahls version, intakes from food were below recommendations for vitamin D, choline and calcium, while several people exceeded safe upper limits for some nutrients once their supplements were counted (Titcomb et al., 2020). Whether a particular version meets a particular person's needs is a question for a registered dietitian.

Who should not follow it without medical supervision

Anyone who is pregnant, breastfeeding or planning a pregnancy, because the diet removes major sources of iodine and calcium and iodine needs rise in pregnancy (Manousou et al., 2018; National Institutes of Health Office of Dietary Supplements, 2024). Anyone with low bone density, a history of fractures or a high risk of osteoporosis, a group the Nutrition Source names among its unanswered questions (Harvard T.H. Chan School of Public Health, n.d.). Anyone with a thyroid condition, given the iodine finding. Anyone with kidney disease, because how much protein and potassium is right depends on the stage of the disease, lab results and whether the person is on dialysis; the kidney care team decides, and the pattern's fruit and vegetables are not a hazard for everyone with kidney disease.

Anyone taking insulin, a sulfonylurea, blood pressure medication or warfarin, for the reasons under medication interactions below. Anyone with high LDL cholesterol or heart disease who plans to eat a version heavy in fatty meat. Children, whose calcium needs are high and for whom no trial was found. And anyone with a history of disordered eating, where a list of foods the body supposedly cannot handle can become a set of rules.

Medication interactions

A coach never adjusts medication. The point of knowing these is to know when to send a client back to the prescriber. The diet can lower blood sugar, blood pressure and weight, so a client on insulin, a sulfonylurea or blood pressure medication who plans a substantial change in eating keeps the prescriber informed before making it, and a possible low blood sugar episode is treated first under the client's own plan.

Some widely prescribed blood pressure medications raise blood potassium and can require potassium restriction (Palmer & Clegg, 2016), which matters on a diet rich in fruit and vegetables. People taking warfarin need a steady vitamin K intake, and a large increase in leafy greens can change how the drug works (National Institutes of Health Office of Dietary Supplements, 2021). A client who starts calcium or iodine supplements because of this diet should ask the prescriber or pharmacist whether they interact with their other medications.

Signs it is going wrong

Physical signs a coach or a family member might notice are shakiness, sweating or confusion between meals in someone on diabetes medication; dizziness on standing in someone on blood pressure medication; ongoing digestive changes; a swelling at the front of the neck; a broken bone from a minor fall; lasting tiredness; and weight loss the person did not intend. Each is a reason to involve a clinician, not a diagnosis. The coach notices and encourages the client to tell their clinician, and working out the cause is the clinician's job.

Behavior matters as much, and has to be read with care. Cutting grains or dairy can come from celiac disease, an allergy, lactose intolerance, a cultural or religious practice or a dietitian's plan, so on its own it tells a coach little. Talk of grains or dairy as poison, a growing list of forbidden foods, anxiety or guilt after eating outside the rules, or turning down meals with family and friends carries more meaning and is worth asking about directly. The questions are the same in every case: what the behavior is for, whether it causes distress, whether it is narrowing what the person eats, and whether it is getting in the way of daily life. None of this is a diagnosis. Where the answers raise a real concern about disordered eating, the coach follows their own referral process.

Myths and where they came from

Myth: humans have not evolved to eat grains, dairy or beans

Where it came from: the evolutionary discordance hypothesis published in 1985 and the popular books built on it, which argue that farming arrived too recently for the body to adapt (Cordain et al., 2005; The Paleo Diet Team, n.d.-a). What is true: its own authors presented it as a source of hypotheses to be tested, not a finding (Konner & Eaton, 2010). The 2015 review notes that there was no single Paleolithic diet, because food choices depended on latitude and climate (Manheimer et al., 2015), and the Nutrition Source notes that there is no one "true" Paleo diet and that modern fruits and vegetables bear little resemblance to wild ones (Harvard T.H. Chan School of Public Health, n.d.). The American Heart Association's guidance includes whole grains and legumes as features of a heart-healthy pattern (Lichtenstein et al., 2026).

Myth: paleo is proven to prevent heart disease and diabetes

Where it came from: early trials that showed large improvements in blood sugar and blood fats, and cohort studies linking higher paleo scores with lower death rates. What is true: the trials were small and short and measured risk factors, not disease, and the searches for this page found no trial that measured heart attacks, diabetes or death. Pooled trials did not show a clear difference in blood sugar control against other healthy diets (Jamka et al., 2020). The cohort studies scored ordinary diets, and in one the association depended largely on avoiding ultra-processed food (de la O et al., 2022).

Myth: paleo means eating lots of meat

Where it came from: the caveman image and the popular versions built around steak and bacon. What is true: the founder's organization says the diet is primarily plant-based by volume (The Paleo Diet Team, n.d.-a), and the trial diets used lean meat and fish with plenty of vegetables. The American Heart Association, describing how the pattern is popularly followed, says it tends to be high in saturated fat (Gardner et al., 2023). Both describe real versions; which one a client is eating is the question that matters.

Myth: if the diet works, you have to stay 100 percent strict

Where it came from: the all-or-nothing tone of many popular programs. What is true: the founder's own organization recommends an 85/15 approach and says people can benefit while eating paleo for only part of their meals (McNew, n.d.). The trials themselves rarely achieved full adherence: in the 2-year trial, the paleo group never reached its protein target (Mellberg et al., 2014).

7. Key terms

Paleolithic era

The long stretch of human prehistory before farming began, ending about 10,000 years ago, when people lived by hunting, fishing and gathering.

Evolutionary discordance hypothesis

The idea that a mismatch between the conditions humans evolved in and modern diets and lifestyles contributes to chronic disease. It is a hypothesis, not an established finding.

Ad libitum

Eating as much as you want. Most paleo trials gave advice about which foods to eat without limiting amounts.

Metabolic syndrome

A cluster of risk factors: a large waist, high triglycerides, low HDL cholesterol, high blood pressure and high fasting blood sugar. Having several raises the risk of diabetes and heart disease.

Triglycerides

A type of fat in the blood. High levels are one of the features of the metabolic syndrome.

LDL cholesterol

The cholesterol carried in low-density lipoprotein, which builds up in artery walls. Diets high in saturated fat tend to raise it.

HbA1c

A blood test that reflects average blood sugar over the previous few months. Interpreting a result belongs to a clinician.

Crossover trial

A trial in which each person eats both diets, one after the other in random order, so that each person serves as their own comparison.

Paleo diet score

A number researchers calculate from a food questionnaire to rank how closely a person's ordinary eating resembles the paleo pattern. It measures resemblance, not whether someone follows the diet.

Hazard ratio

A measure from studies that follow people over time: how much more or less often an event happens per unit of time in one group than in another. A hazard ratio of 0.77 means events happened about 23 percent less often.

GRADE

The 4-level scale used in clinical guidelines to say how certain the evidence for a conclusion is: high, moderate, low or very low. It rates the evidence for one outcome at a time, not the diet.

Network meta-analysis

A review method that compares many diets at once by linking trials that share a comparison diet, so that diets never tested against each other can still be compared indirectly.

8. Review questions

1. Name the 3 food groups the paleo diet removes that most heart-health guidance keeps, and explain how the diet's promoters justify removing them. Which part of their reasoning is a hypothesis rather than a finding?
2. The paleo trials compared the diet with diets based on national healthy eating guidance, not with typical Western eating. What did they find for waist size and triglycerides, over how long, and in whom? What did the 2-year trial add? (This question draws on section 4.)
3. A client who takes insulin tells you she has gone paleo and cut out bread, rice and potatoes, and that she has felt shaky before lunch twice in the past few days. What does the coach do, in what order, and where is the referral line?
4. A client says paleo is proven to prevent heart disease because studies show paleo eaters live longer. Where does that belief come from, and what do those studies measure? (This question draws on sections 4 and 6.)

9. References

Ahlgren, C., Hammarström, A., Sandberg, S., Lindahl, B., Olsson, T., Larsson, C., & Fjellman-Wiklund, A. (2016). Engagement in new dietary habits: Obese women's experiences from participating in a 2-year diet intervention. International Journal of Behavioral Medicine, 23(1), 84-93. https://doi.org/10.1007/s12529-015-9495-x

Bahrami, M., Bakhshimoghaddam, F., Ahangarpour, A., & Jafarirad, S. (2026). The Paleolithic diet and chronic disease risk: A GRADE-assessed systematic review and dose-response meta-analysis of prospective cohort studies and randomized controlled trials. Critical Reviews in Food Science and Nutrition, 66(11), 2247-2262. https://doi.org/10.1080/10408398.2025.2576815

Boers, I., Muskiet, F. A., Berkelaar, E., Schut, E., Penders, R., Hoenderdos, K., Wichers, H. J., & Jong, M. C. (2014). Favourable effects of consuming a Palaeolithic-type diet on characteristics of the metabolic syndrome: A randomized controlled pilot-study. Lipids in Health and Disease, 13, Article 160. https://doi.org/10.1186/1476-511X-13-160

Chen, X., Dickinson, S. L., & Allison, D. B. (2020). Errors in meta-analysis should be corrected: Comment on "Effects of a Paleolithic Diet on Cardiovascular Disease Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials" [Letter to the editor]. Advances in Nutrition, 11(4), 1047-1048. https://doi.org/10.1093/advances/nmaa035

Cordain, L., Eaton, S. B., Sebastian, A., Mann, N., Lindeberg, S., Watkins, B. A., O'Keefe, J. H., & Brand-Miller, J. (2005). Origins and evolution of the Western diet: Health implications for the 21st century. The American Journal of Clinical Nutrition, 81(2), 341-354. https://doi.org/10.1093/ajcn.81.2.341

de la O, V., Zazpe, I., Goni, L., Santiago, S., Martín-Calvo, N., Bes-Rastrollo, M., Martínez, J. A., Martínez-González, M. Á., & Ruiz-Canela, M. (2022). A score appraising Paleolithic diet and the risk of cardiovascular disease in a Mediterranean prospective cohort. European Journal of Nutrition, 61(2), 957-971. https://doi.org/10.1007/s00394-021-02696-9

Effects of a Paleolithic diet on cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled trials [Correction]. (2020). Advances in Nutrition, 11(4), 1054. https://doi.org/10.1093/advances/nmaa033

Fontes-Villalba, M., Fika-Hernando, M. L., Picazo, Ó., Frassetto, L. A., Carrera-Bastos, P., Memon, A. A., Lippi, G., Montagnana, M., Granfeldt, Y., Sundquist, K., Sundquist, J., & Jönsson, T. (2025). Randomised crossover controlled trial of dietary interventions for glycaemic control when body weight is kept stable. Journal of Nutritional Science, 14, Article e59. https://doi.org/10.1017/jns.2025.10028

Frączek, B., Pięta, A., Burda, A., Mazur-Kurach, P., & Tyrała, F. (2021). Paleolithic diet: Effect on the health status and performance of athletes? Nutrients, 13(3), Article 1019. https://doi.org/10.3390/nu13031019

Gardner, C. D., Vadiveloo, M. K., Petersen, K. S., Anderson, C. A. M., Springfield, S., Van Horn, L., Khera, A., Lamendola, C., Mayo, S. M., & Joseph, J. J. (2023). Popular dietary patterns: Alignment with American Heart Association 2021 dietary guidance: A scientific statement from the American Heart Association. Circulation, 147(22), 1715-1730. https://doi.org/10.1161/CIR.0000000000001146

Genoni, A., Christophersen, C. T., Lo, J., Coghlan, M., Boyce, M. C., Bird, A. R., Lyons-Wall, P., & Devine, A. (2020). Long-term Paleolithic diet is associated with lower resistant starch intake, different gut microbiota composition and increased serum TMAO concentrations. European Journal of Nutrition, 59(5), 1845-1858. https://doi.org/10.1007/s00394-019-02036-y

Genoni, A., Lo, J., Lyons-Wall, P., & Devine, A. (2016). Compliance, palatability and feasibility of Paleolithic and Australian Guide to Healthy Eating diets in healthy women: A 4-week dietary intervention. Nutrients, 8(8), Article 481. https://doi.org/10.3390/nu8080481

Genoni, A., Lyons-Wall, P., Lo, J., & Devine, A. (2016). Cardiovascular, metabolic effects and dietary composition of ad-libitum Paleolithic vs. Australian Guide to Healthy Eating diets: A 4-week randomised trial. Nutrients, 8(5), Article 314. https://doi.org/10.3390/nu8050314

Ghaedi, E., Mohammadi, M., Mohammadi, H., Ramezani-Jolfaie, N., Malekzadeh, J., Hosseinzadeh, M., & Salehi-Abargouei, A. (2019). Effects of a Paleolithic diet on cardiovascular disease risk factors: A systematic review and meta-analysis of randomized controlled trials. Advances in Nutrition, 10(4), 634-646. (Corrected and republished version.) https://doi.org/10.1093/advances/nmz007

Ghaedi, E., Mohammadi, M., Mohammadi, H., Ramezani-Jolfaie, N., Malekzadeh, J., Hosseinzadeh, M., & Salehi-Abargouei, A. (2020). Reply to X Chen et al. [Letter to the editor]. Advances in Nutrition, 11(4), 1048-1050. https://doi.org/10.1093/advances/nmaa036

Harvard T.H. Chan School of Public Health. (n.d.). Diet review: Paleo diet for weight loss. The Nutrition Source. nutritionsource.hsph.harvard.edu/healthy-weight/diet-reviews/paleo-diet

Irish, A. K., Erickson, C. M., Wahls, T. L., Snetselaar, L. G., & Darling, W. G. (2017). Randomized control trial evaluation of a modified Paleolithic dietary intervention in the treatment of relapsing-remitting multiple sclerosis: A pilot study. Degenerative Neurological and Neuromuscular Disease, 7, 1-18. https://doi.org/10.2147/DNND.S116949

Jamka, M., Kulczyński, B., Juruć, A., Gramza-Michałowska, A., Stokes, C. S., & Walkowiak, J. (2020). The effect of the Paleolithic diet vs. healthy diets on glucose and insulin homeostasis: A systematic review and meta-analysis of randomized controlled trials. Journal of Clinical Medicine, 9(2), Article 296. https://doi.org/10.3390/jcm9020296

Jones, L. (2026, January 8). Paleo diet. U.S. News & World Report. health.usnews.com/best-diet/paleo-diet

Jönsson, T., Granfeldt, Y., Ahrén, B., Branell, U. C., Pålsson, G., Hansson, A., Söderström, M., & Lindeberg, S. (2009). Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes: A randomized cross-over pilot study. Cardiovascular Diabetology, 8, Article 35. https://doi.org/10.1186/1475-2840-8-35

Karlsen, M. C., Lichtenstein, A. H., Economos, C. D., Folta, S. C., Chang, R., Rogers, G., Jacques, P. F., Livingston, K. A., & McKeown, N. M. (2020). Participant characteristics and self-reported weight status in a cross-sectional pilot survey of self-identified followers of popular diets: Adhering to Dietary Approaches for Personal Taste (ADAPT) Feasibility Survey. Public Health Nutrition, 23(15), 2717-2727. https://doi.org/10.1017/S1368980020001330

Konner, M., & Eaton, S. B. (2010). Paleolithic nutrition: Twenty-five years later. Nutrition in Clinical Practice, 25(6), 594-602. https://doi.org/10.1177/0884533610385702

Lavie, M., Lavie, I., & Maslovitz, S. (2019). Paleolithic diet during pregnancy: A potential beneficial effect on metabolic indices and birth weight. European Journal of Obstetrics & Gynecology and Reproductive Biology, 242, 7-11. https://doi.org/10.1016/j.ejogrb.2019.08.013

Lee, J. E., Titcomb, T. J., Bisht, B., Rubenstein, L. M., Louison, R., & Wahls, T. L. (2021). A modified MCT-based ketogenic diet increases plasma β-hydroxybutyrate but has less effect on fatigue and quality of life in people with multiple sclerosis compared to a modified Paleolithic diet: A waitlist-controlled, randomized pilot study. Journal of the American College of Nutrition, 40(1), 13-25. https://doi.org/10.1080/07315724.2020.1734988

Lichtenstein, A. H., Khera, A., Anderson, C. A. M., Appel, L. J., DeSilva, D. M., Gardner, C., Hu, F. B., Jones, D. W., Petersen, K. S., & American Heart Association. (2026). 2026 dietary guidance to improve cardiovascular health: A scientific statement from the American Heart Association. Circulation, 153(18), e1285-e1295. https://doi.org/10.1161/CIR.0000000000001435

Lindeberg, S., Jönsson, T., Granfeldt, Y., Borgstrand, E., Soffman, J., Sjöström, K., & Ahrén, B. (2007). A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischaemic heart disease. Diabetologia, 50(9), 1795-1807. https://doi.org/10.1007/s00125-007-0716-y

Manheimer, E. W., van Zuuren, E. J., Fedorowicz, Z., & Pijl, H. (2015). Paleolithic nutrition for metabolic syndrome: Systematic review and meta-analysis. The American Journal of Clinical Nutrition, 102(4), 922-932. https://doi.org/10.3945/ajcn.115.113613

Manousou, S., Stål, M., Larsson, C., Mellberg, C., Lindahl, B., Eggertsen, R., Hulthén, L., Olsson, T., Ryberg, M., Sandberg, S., & Nyström, H. F. (2018). A Paleolithic-type diet results in iodine deficiency: A 2-year randomized trial in postmenopausal obese women. European Journal of Clinical Nutrition, 72(1), 124-129. https://doi.org/10.1038/ejcn.2017.134

Masharani, U., Sherchan, P., Schloetter, M., Stratford, S., Xiao, A., Sebastian, A., Nolte Kennedy, M., & Frassetto, L. (2015). Metabolic and physiologic effects from consuming a hunter-gatherer (Paleolithic)-type diet in type 2 diabetes. European Journal of Clinical Nutrition, 69(8), 944-948. https://doi.org/10.1038/ejcn.2015.39

McNew, A. (n.d.). Explaining The Paleo Diet 85/15 principle. The Paleo Diet. thepaleodiet.com/explaining-the-85-15-principle

Mellberg, C., Sandberg, S., Ryberg, M., Eriksson, M., Brage, S., Larsson, C., Olsson, T., & Lindahl, B. (2014). Long-term effects of a Palaeolithic-type diet in obese postmenopausal women: A 2-year randomized trial. European Journal of Clinical Nutrition, 68(3), 350-357. https://doi.org/10.1038/ejcn.2013.290

Metzgar, M., Rideout, T. C., Fontes-Villalba, M., & Kuipers, R. S. (2011). The feasibility of a Paleolithic diet for low-income consumers. Nutrition Research, 31(6), 444-451. https://doi.org/10.1016/j.nutres.2011.05.008

National Institutes of Health Office of Dietary Supplements. (2021, March 22). Vitamin K: Fact sheet for consumers. ods.od.nih.gov/factsheets/VitaminK-Consumer

National Institutes of Health Office of Dietary Supplements. (2023, September 14). Calcium: Fact sheet for consumers. ods.od.nih.gov/factsheets/Calcium-Consumer

National Institutes of Health Office of Dietary Supplements. (2024, May 1). Iodine: Fact sheet for consumers. ods.od.nih.gov/factsheets/Iodine-Consumer

Norwood, R., Cruwys, T., Chachay, V. S., & Sheffield, J. (2019). The psychological characteristics of people consuming vegetarian, vegan, paleo, gluten free and weight loss dietary patterns. Obesity Science & Practice, 5(2), 148-158. https://doi.org/10.1002/osp4.325

O'Malley, K., Willits-Smith, A., & Rose, D. (2023). Popular diets as selected by adults in the United States show wide variation in carbon footprints and diet quality. The American Journal of Clinical Nutrition, 117(4), 701-708. https://doi.org/10.1016/j.ajcnut.2023.01.009

Otten, J., Stomby, A., Waling, M., Isaksson, A., Tellström, A., Lundin-Olsson, L., Brage, S., Ryberg, M., Svensson, M., & Olsson, T. (2017). Benefits of a Paleolithic diet with and without supervised exercise on fat mass, insulin sensitivity, and glycemic control: A randomized controlled trial in individuals with type 2 diabetes. Diabetes/Metabolism Research and Reviews, 33(1), Article e2828. https://doi.org/10.1002/dmrr.2828

The Paleo Diet. (n.d.). The Paleo Diet: The strong and healthy diet. thepaleodiet.com

The Paleo Diet Team. (n.d.-a). The benefits of The Paleo Diet. The Paleo Diet. thepaleodiet.com/benefits-of-the-paleo-diet

The Paleo Diet Team. (n.d.-b). What can you eat on The Paleo Diet? The Paleo Diet. thepaleodiet.com/what-can-you-eat-on-the-paleo-diet

The Paleo Diet Team. (2022, May 23). The Paleo Diet marks 20-year anniversary [Press release]. The Paleo Diet. thepaleodiet.com/the-paleo-diet-marks-20-year-anniversary

Palmer, B. F., & Clegg, D. J. (2016). Achieving the benefits of a high-potassium, Paleolithic diet, without the toxicity. Mayo Clinic Proceedings, 91(4), 496-508. https://doi.org/10.1016/j.mayocp.2016.01.012

Pastore, R. L., Brooks, J. T., & Carbone, J. W. (2015). Paleolithic nutrition improves plasma lipid concentrations of hypercholesterolemic adults to a greater extent than traditional heart-healthy dietary recommendations. Nutrition Research, 35(6), 474-479. https://doi.org/10.1016/j.nutres.2015.05.002

Pięta, A., Frączek, B., Wiecek, M., & Mazur-Kurach, P. (2023). Impact of Paleo diet on body composition, carbohydrate and fat metabolism of professional handball players. Nutrients, 15(19), Article 4155. https://doi.org/10.3390/nu15194155

Popp, C. J., Bohan Brown, M. M., Bridges, W. C., & Jesch, E. D. (2018). The effectiveness of MyPlate and Paleolithic-based diet recommendations, both with and without exercise, on aerobic fitness, muscular strength and anaerobic power in young women: A randomized clinical trial. International Journal of Exercise Science, 11(2), 921-933. https://doi.org/10.70252/SHUV3305

Rydhög, B., Carrera-Bastos, P., Granfeldt, Y., Sundquist, K., Sonestedt, E., Nilsson, P. M., & Jönsson, T. (2024). Inverse association between Paleolithic Diet Fraction and mortality and incidence of cardiometabolic disease in the prospective Malmö Diet and Cancer Study. European Journal of Nutrition, 63(2), 501-512. https://doi.org/10.1007/s00394-023-03279-6

Schwingshackl, L., Chaimani, A., Hoffmann, G., Schwedhelm, C., & Boeing, H. (2018). A network meta-analysis on the comparative efficacy of different dietary approaches on glycaemic control in patients with type 2 diabetes mellitus. European Journal of Epidemiology, 33(2), 157-170. https://doi.org/10.1007/s10654-017-0352-x

Schwingshackl, L., Chaimani, A., Schwedhelm, C., Toledo, E., Pünsch, M., Hoffmann, G., & Boeing, H. (2019). Comparative effects of different dietary approaches on blood pressure in hypertensive and pre-hypertensive patients: A systematic review and network meta-analysis. Critical Reviews in Food Science and Nutrition, 59(16), 2674-2687. https://doi.org/10.1080/10408398.2018.1463967

Sohouli, M. H., Fatahi, S., Lari, A., Lotfi, M., Seifishahpar, M., Găman, M. A., Rahideh, S. T., AlBatati, S. K., AlHossan, A. M., Alkhalifa, S. A., Alomar, S. A., & Abu-Zaid, A. (2022). The effect of paleolithic diet on glucose metabolism and lipid profile among patients with metabolic disorders: A systematic review and meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition, 62(17), 4551-4562. https://doi.org/10.1080/10408398.2021.1876625

Titcomb, T. J., Bisht, B., Moore, D. D., Chhonker, Y. S., Murry, D. J., Snetselaar, L. G., & Wahls, T. L. (2020). Eating pattern and nutritional risks among people with multiple sclerosis following a modified Paleolithic diet. Nutrients, 12(6), Article 1844. https://doi.org/10.3390/nu12061844

Wahls, T. L., Titcomb, T. J., Bisht, B., Eyck, P. T., Rubenstein, L. M., Carr, L. J., Darling, W. G., Hoth, K. F., Kamholz, J., & Snetselaar, L. G. (2021). Impact of the Swank and Wahls elimination dietary interventions on fatigue and quality of life in relapsing-remitting multiple sclerosis: The WAVES randomized parallel-arm clinical trial. Multiple Sclerosis Journal: Experimental, Translational and Clinical, 7(3), Article 20552173211035399. https://doi.org/10.1177/20552173211035399

Whalen, K. A., Judd, S., McCullough, M. L., Flanders, W. D., Hartman, T. J., & Bostick, R. M. (2017). Paleolithic and Mediterranean diet pattern scores are inversely associated with all-cause and cause-specific mortality in adults. The Journal of Nutrition, 147(4), 612-620. https://doi.org/10.3945/jn.116.241919

Xiao, Y., Wang, Y., Gu, H., Xu, Z., Tang, Y., He, H., Peng, L., & Xiang, L. (2023). Adherence to the Paleolithic diet and Paleolithic-like lifestyle reduce the risk of colorectal cancer in the United States: A prospective cohort study. Journal of Translational Medicine, 21(1), Article 482. https://doi.org/10.1186/s12967-023-04352-8

Zdzieblik, D., Waldvogel, T., Zierke, A., Gollhofer, A., & König, D. (2024). Effect of a modern Palaeolithic diet in combination with a sprint interval training on metabolic and performance-related parameters in male athletes: A pilot trial. Nutrition and Metabolic Insights, 17, Article 11786388241299896. https://doi.org/10.1177/11786388241299896

Evidence rating and review record

Each row identifies the method, source, outcome or recommendation, and comparison being rated. Ratings from different tools are not interchangeable. The source is either a named published review or this page's own judgment. The rating in the banner is for this diet's main claimed outcome or recommendation, and the banner names the tool that produced it. A high rating means the research is solid; it does not mean the diet is right for everyone, and it does not mean a coach should recommend it.

The rated outcomes on this page use GRADE. Each row identifies its source or this page's own judgment and the comparison being rated. Rows rated with GRADE use the same 4-level scale as the clinical guidelines you will meet in practice. High means further research is very unlikely to change the conclusion. Moderate means further research may change it. Low means further research is likely to change it. Very low means the conclusion is uncertain. GRADE rates each outcome separately, so a diet can be high for one outcome and very low for another. A row marked Not rated is an abstention, not a certainty level.

Three things about this table matter before reading it. The first 5 rows are published ratings from one 2015 review of 4 short trials, reported exactly as published; they rate changes in risk factors over up to 6 months against diets based on national guidelines, not prevention of disease. The rows marked as this page's own judgment were assigned from the evidence given in each row's reasons. And the diet's central claim, that it prevents chronic disease, has no rating, because no trial found for this page measured disease.

On a narrow screen, scroll the table sideways to see every column.

Evidence ratings, their sources and reasons

Outcome	Certainty	Who rated it, and for which comparison	Why it is rated this way
Waist circumference, short term	Moderate	Manheimer et al., 2015, using GRADE. Paleo diets against diets based on national guidelines, in adults with at least one feature of the metabolic syndrome; 4 randomized trials, 137 people analyzed; first measurement at 2 to 26 weeks	2.38 cm lower, from 0.04 to 4.73 cm lower. The reviewers started at high and lowered 1 level for imprecision, because the interval comes very close to no effect. Reported exactly as published; the review covers trials published to January 2015.
Triglycerides, short term	Moderate	Manheimer et al., 2015, using GRADE. Same comparison, 4 trials, 137 people	0.40 mmol/L lower, from 0.04 to 0.76 lower. Lowered 1 level for inconsistency, because one trial showed a different direction of effect and the heterogeneity statistic (I²) was 73 percent.
Systolic and diastolic blood pressure, short term	Moderate for each	Manheimer et al., 2015, using GRADE. Same comparison, 4 trials, 137 people	Systolic 3.64 mm Hg lower, from 7.36 lower to 0.08 higher; diastolic 2.48 mm Hg lower, from 4.98 lower to 0.02 higher. Each lowered 1 level for imprecision. Both intervals reach no difference.
HDL cholesterol and fasting blood sugar, short term	Moderate for each	Manheimer et al., 2015, using GRADE. Same comparison; 3 trials, 108 people, for HDL cholesterol and 4 trials, 137 people, for fasting blood sugar	No clear difference was detected for either: HDL cholesterol 0.12 mmol/L higher, from 0.03 lower to 0.28 higher; fasting blood sugar 0.16 mmol/L lower, from 0.44 lower to 0.11 higher. Each lowered 1 level for imprecision. The rating is for the estimate, not for an advantage.
Body weight, as measured, short term	Moderate	Manheimer et al., 2015, using GRADE. Same comparison, 4 trials, 137 people	2.69 kg lower, from 0.52 to 4.87 kg lower. Lowered 1 level for imprecision. Reported as a measurement, not as a goal.
LDL cholesterol, short term	Low	This page's own judgment, using GRADE. Paleo diets against healthy comparison diets, 5 randomized trials pooled in the corrected review by Ghaedi et al., 2019, with the 2-year trial (Mellberg et al., 2014) read alongside	Trials start high. Lowered 1 level for risk of bias, for reasons specific to these trials: allocation protection is uncertain (the 2019 review judged allocation concealment unclear in every trial it included, while the 2015 review judged it adequate in the 3 of these trials it also included); one trial had a clear baseline imbalance that the 2015 review judged high risk (Boers et al., 2014); and by 6 months, the time point used, the 2-year trial had lost 8 women from the comparison group and 1 from the paleo group (Manheimer et al., 2015). Knowing their diet could change what participants ate beyond the assigned diet, although a laboratory LDL result is less open to expectation than a self-reported outcome. Lowered 1 level for imprecision: the estimate, 0.13 mmol/L lower, from 0.26 to 0.01 lower, sits close to no difference, the trials were small, removing any one of 3 trials made the result uncertain, and the corrected analysis lost statistical significance under a different assumed correlation for estimating standard deviations (Ghaedi et al., 2019). Inconsistency not serious (I² was 0 percent). Indirectness not serious for the versions tested, which used lean meat and unsaturated fats; the rating does not extend to versions heavy in saturated fat. One test suggested missing small studies and a correction changed the estimate little; with 5 trials that test is weak, so it was not counted separately. The rating supports "little change or a small fall," not a clear benefit.
Blood sugar control in people with impaired glucose metabolism	Low	This page's own judgment, using GRADE. Paleo diets against Mediterranean, diabetes and Dutch guideline diets, 4 randomized trials, 98 people (Jamka et al., 2020), with the weight-stable trial (Fontes-Villalba et al., 2025) read alongside	Trials start high. Lowered 1 level for risk of bias, for reasons specific to these trials: allocation protection is uncertain (the 2020 review judged allocation concealment high risk in all 4 trials, while the 2015 review judged it adequate in the 3 it shared); the 2020 review notes a significant baseline difference between groups in one trial (Jönsson et al., 2009); and the 12-week Swedish trial left out 9 randomized men after allocation, 3 of them from the paleo group for unwillingness to continue (Lindeberg et al., 2007). Knowing their diet could change adherence and other eating, although laboratory blood sugar measures are less open to expectation than self-reported outcomes. Lowered 1 level for imprecision, because the trials were very small and the intervals wide. Inconsistency and indirectness not serious. Publication bias could not be assessed with 4 trials. No clear difference was detected; this is not evidence that the diets are equivalent. The weight-stable trial did not demonstrate a clear difference in HbA1c over 4 weeks and does not remove that uncertainty.
Long-term body composition and triglyceride effects, applied to adults generally	Very low	This page's own judgment, using GRADE. Paleo diet against the Nordic Nutrition Recommendations, applied to adults generally; the evidence is 1 randomized trial in 70 women after menopause with obesity in Sweden, followed for 2 years (Mellberg et al., 2014)	Trials start high. Lowered 1 level for risk of bias, because 30 percent were lost to follow-up, unevenly between groups, and the paleo group did not reach its protein target. Lowered 1 level for imprecision, because it is a single small trial. Lowered 1 level for indirectness, because one narrow group of women is being used to judge effects in adults generally; for the population the trial enrolled, this deduction would not apply and the rating would be Low. Inconsistency and publication bias cannot be judged from one trial. At 24 months the triglyceride difference remained and the fat mass difference was not clear.
Fatigue in relapsing-remitting multiple sclerosis	Very low	This page's own judgment, using GRADE. The modified Paleolithic (Wahls) diet against usual diet in relapsing-remitting multiple sclerosis: 1 partly randomized pilot trial, 34 allocated, 19 completing follow-up and 17 in the primary per-protocol analysis (Irish et al., 2017), with the Wahls against Swank trial (Wahls et al., 2021) read alongside	Trials start high. Lowered 2 levels for risk of bias: after the first 5 in each group, participants were assigned by fatigue score rather than by chance; participants knew their diet and fatigue is self-reported; 2 diet-group participants were left out of the primary analysis after allocation for not keeping to the diet; and 15 of the 34 allocated did not complete follow-up. Lowered 1 level for imprecision, because of the very small number analyzed. Very low is the lowest level, so these concerns cannot lower it further. The larger trial compared 2 diets without a usual-diet group, so it cannot raise the rating, and a pilot in mostly progressive multiple sclerosis (Lee et al., 2021) is a separate comparison. Reported for this one condition only.
Heart attack, stroke, new diabetes, cancer or death, in trials	Not rated	This page's own judgment. No comparison is possible	The searches for this page found no randomized trial of the paleo diet that measured any of these outcomes. This is a statement about the trials found, not a finding of no effect.
Death from any cause, in people whose ordinary eating scores closer to the pattern	Very low, for an association	This page's own judgment, using GRADE. Highest against lowest paleo score, or a continuous score, in prospective cohorts: REGARDS, 21,423 adults (Whalen et al., 2017); Malmö Diet and Cancer, 24,104 adults (Rydhög et al., 2024)	Cohort studies start low. Lowered 1 level for risk of bias specific to these studies: both measured diet once, at the start; their questionnaires characterize healthy behaviors and food details incompletely, which the REGARDS authors name as a source of residual confounding; and the Swedish cohort's 18-year follow-up cannot account for changes in eating over time, a limitation its authors name (Rydhög et al., 2024; Whalen et al., 2017). The general limitation of any nonrandomized study is already reflected in the low starting point and is not counted again. Inconsistency not serious: both cohorts point the same way. Indirectness not serious for the association as rated, which is between ordinary-diet scores and death, not between following the diet and death. Imprecision not serious. Publication bias cannot be judged from 2 cohorts. Not raised for a large effect, because confounding by other healthy habits cannot be ruled out, and in a related cohort the association depended largely on avoiding ultra-processed food (de la O et al., 2022). A 2026 review's pooled cohort estimate is not used, for the reasons given in section 4. The rating is for the direction of an association, not for an effect of following the diet.

How this archive talks about weight. This page reports what studies measured, including body weight, and does not treat weight change as a goal or as a measure of a diet's success. Weight a person loses without meaning to can be a sign of a health problem, and where it is, the page names it as a reason to see a clinician. People are described the way the study described them.

Last reviewed: Reviewed and approved by James Peth, MS, MPH, PhD, on October 4, 2026, after a combined final review of the second batch of 5 archive pages, the repairs it asked for and a targeted recheck. Written October 3, 2026.

What changed: The comparison and absence statements were corrected, and 2 studies were added (Lee et al., 2021; Pięta et al., 2023). The multiple sclerosis pilot is now described as partly randomized. A 2026 review is no longer used to set any rating, because of problems found in its full text. The reasons for several ratings that are this page's own judgment were rewritten, with every label unchanged and each GRADE domain recorded in the page's claim ledger. The cost paragraph was narrowed to what its modeling study shows, and the company references were corrected. Two reviews cited here, from 2019 and 2022, and the 2-year trial's iodine report could be read only as abstracts. After the outside recheck, the 2022 review is described as including 10 articles, the count its abstract gives. The scope box now lists 8 groups needing medical oversight.

Updated October 21, 2026: The American Heart Association is now named as an author of its 2026 dietary guidance statement (Lichtenstein et al., 2026), as the publisher's citation credits it. No content changed.

Next scheduled review: August 2027. Pages built on annual guidance are rechecked each year. The federal fact sheets cited on this page are updated from time to time and should be rechecked first.

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Diet Reference Archive | One James

Prepared by James Peth, MS, MPH, PhD

© 2026–2027 One James. All rights reserved.

This page is for education and coaching practice. It is not medical or dietary advice.