Does the paleo diet work? What it gets right, and what it gets wrong

A healthy adult, no celiac disease, digests milk without trouble. He goes strict paleo. A few weeks in, his fibre intake is low, his grocery bill is up, and every dinner with friends turns into a negotiation. What has he gained? Compared with a whole-food diet that still includes oats, lentils and yogurt, nothing measurable.

That case vignette sits at the centre of my book The Paleolithic Ancestral Diet, and it captures the question most people ask about the paleo diet: does it work, and if so, why? My answer, in short: the paleo diet is two things wearing one name. One of them is sound. The other is oversold.

What is the paleo diet, exactly?

The paleo diet includes foods presumed available to pre-agricultural humans: meat, fish, eggs, vegetables, fruit, roots and tubers, nuts and seeds. It excludes foods introduced by agriculture and industry: grains (whole grains included), legumes such as beans, lentils, peanuts and soy, dairy, refined sugar, refined seed oils and processed foods.

Several variants share the name:

• Whole30, a strict 30-day elimination meant as a "reset", followed by structured reintroduction;
• Primal, which permits some dairy, especially full-fat and fermented;
• The autoimmune protocol (AIP), a stricter elimination that also removes eggs, nightshades, nuts and seeds, and belongs in clinical hands;
• The "ancestral" lifestyle, which bundles paleo eating with sleep, movement and sun exposure.

One point often surprises people: paleo is usually higher in protein and lower in refined carbohydrate than a Western diet, but it is not necessarily low-carb.

Is the paleo diet healthy? Two layers, one name

In the book, I separate paleo into two layers.

1. The food-quality layer. Eat whole, minimally processed foods; cut ultra-processed food, refined sugar, refined grains and industrial oils. This is well supported, and it overlaps with every evidence-based pattern, Mediterranean included.
2. The ancestral-justification layer. We should eat this way because it matches the diet our genes evolved for, and grains, legumes and dairy are "discordant" with our biology. This rests on the evolutionary-discordance hypothesis, which is an oversimplification.

Why an oversimplification? There was no single Paleolithic diet: ancestral diets varied enormously by place and season. And humans kept evolving after agriculture. Lactase persistence, the trait that lets billions of adults digest milk, is the clearest example. "Our ancestors didn't eat it" is a weak basis for a modern food decision.

What does the research say about the paleo diet?

The best-known pooled analysis is the meta-analysis by Manheimer and colleagues (Manheimer et al., 2015). It combined four randomized trials, about 159 participants with features of metabolic syndrome, comparing a Paleolithic diet with guideline-based control diets.

In the short term (six months or less), paleo did better on two of the five metabolic-syndrome components, with statistically significant differences:

• waist circumference, about 2.4 cm lower;
• triglycerides, about 0.4 mmol/L lower.

Blood pressure, HDL cholesterol and fasting glucose moved in the same direction, but those differences were small and not statistically significant. The authors themselves flagged the small number of participants, the short durations, the risk of bias, and control diets that were not always good comparators.

Two questions decide what these results mean.

Better than what? Paleo clearly beats a processed Western diet. Against a genuinely high-quality diet, such as a Mediterranean or whole-food guideline diet, the gap shrinks or disappears.

Because of what? The likely drivers are removing ultra-processed food and sugary drinks, losing weight (higher protein and lower energy density increase satiety), eating more protein, and eating more vegetables and fruit. None of these requires banishing lentils.

Durability matters too. In a two-year randomized trial in postmenopausal women (Mellberg et al., 2014), the paleo group lost more fat at six months (6.5 vs 2.6 kg), but by 24 months the difference was no longer statistically significant (4.6 vs 2.9 kg). Adherence to the protein target was poor. Early differences fade; adherence, not the label, governs long-term results.

Are grains, legumes and dairy bad for you?

This is where paleo's central claim is tested most directly, and the evidence runs the other way.

• Whole grains. In a dose-response meta-analysis of prospective cohorts (Aune et al., 2016), about 90 g of whole grains a day was associated with roughly 22% lower cardiovascular disease risk and lower total mortality. These are associations, not proof of cause, but the real problem is refined grains, not intact whole grains.
• Legumes. Beans, lentils, chickpeas and peas are associated with lower LDL cholesterol, better glycemic control and lower cardiovascular risk (Bazzano et al., 2011; Viguiliouk et al., 2019). Lectins are largely destroyed by proper cooking; phytate modestly lowers mineral absorption, but the net effect of these foods is positive.
• Dairy. For most people, dairy is neutral to beneficial for cardiometabolic health, with fermented dairy such as yogurt looking favourable, and it supplies calcium, protein and iodine.

Real, specific problems exist: celiac disease, wheat allergy, lactose intolerance, diagnosed food allergies. They deserve individual management and, for celiac disease or allergy, a diagnosis before any lifelong exclusion. What the book resists is turning each of them into a rule for everyone. Meanwhile, the exclusions carry costs: less fibre, a risk of low calcium, a higher grocery bill, fewer options and harder adherence.

Is the paleo diet good for athletes?

Carbohydrate is the limiting fuel for high-intensity and glycolytic work: sprints, team sports, heavy training volume. A low-carb paleo diet can blunt performance and recovery in that setting.

Paleo can fuel athletes if it is the higher-carb version. The book's worked example: endurance and high-volume athletes may need about 5 to 10 g of carbohydrate per kilogram per day, which for a 70 kg athlete means roughly 350 to 700 g a day. That is hard to reach on low-carb paleo without grains, but feasible with plenty of tubers and fruit, or by including grains.

There is a second risk. Multiple exclusions can quietly lower total energy intake. Combined with heavy training, that can lead to low energy availability and RED-S, with effects on menstrual function, bone and performance. Menstrual changes, stress fractures or persistent fatigue are red flags that call for a health professional.

How do you follow a flexible paleo-style diet?

The book's last chapter fits in one sentence: keep the core, drop the dogma. Each meal combines:

1. a protein anchor (fish, poultry, eggs, lean meat, and legumes or dairy if you include them);
2. abundant vegetables;
3. whole-food carbohydrate matched to your activity (tubers, fruit, whole grains, legumes);
4. healthy fats (olive oil, nuts, seeds, avocado, fish);
5. as little ultra-processed food and added sugar as possible.

If you start from a strict elimination, reintroduce one food group at a time, dairy, then legumes, then whole grains, over several days each, noting genuine symptoms rather than expectations. For most people, all three come back. And an 80/20 approach is fine: a mostly whole-food diet with occasional flexibility is sustainable and captures the benefit.

If you manage a diagnosed disease, take glucose-lowering or blood-pressure medication, are pregnant, or have a history of disordered eating, these choices belong with your physician or a registered dietitian.

Read the book

In The Paleolithic Ancestral Diet, I go through all 13 chapters of evidence: what our ancestors actually ate, how we are still evolving, the trials, the excluded foods, low-carb, athletes, older adults, marketing myths and orthorexia. The book belongs to The Performance & Human Physiology Encyclopedia, a collection of 93 Netritious books, and it is written for active people, coaches, dietitians and health professionals who want the evidence without the hype.

Frequently asked questions

Is the paleo diet low-carb?

Not necessarily. Paleo is usually lower in refined carbohydrate, but tubers, fruit and honey can make it a higher-carb diet, which is the version athletes need.

Is paleo better than the Mediterranean diet?

The trials do not show it. Paleo beats a processed Western diet, but against a high-quality Mediterranean or whole-food diet, the difference shrinks or disappears.

Do I need to give up grains, legumes and dairy?

For most people, no. The evidence shows they are healthful. Celiac disease, allergies and lactose intolerance call for individual adjustment, ideally after a diagnosis.

Where can I find the book?

The Paleolithic Ancestral Diet is available on Amazon in Kindle format, in English.