Category Archives: Paleo Theory

A “New” Theory of Obesity From Kevin Hall

paleo diet, paleolithic diet, caveman diet

Not Kevin Hall

At Scientific American:

Nutrition researcher Kevin Hall strives to project a Zen-like state of equanimity. In his often contentious field, he says he is more bemused than frustrated by the tendency of other scientists to “cling to pet theories despite overwhelming evidence that they are mistaken.” Some of these experts, he tells me with a sly smile, “have a fascinating ability to rationalize away studies that don’t support their views.”

Among those views is the idea that particular nutrients such as fats, carbs or sugars are to blame for our alarming obesity pandemic. (Globally the prevalence of obesity nearly tripled between 1975 and 2016, according to the World Health Organization. The rise accompanies related health threats that include heart disease and diabetes.) But Hall, who works at the National Institute of Diabetes and Digestive and Kidney Diseases, where he runs the Integrative Physiology section, has run experiments that point fingers at a different culprit. His studies suggest that a dramatic shift in how we make the food we eat—pulling ingredients apart and then reconstituting them into things like frosted snack cakes and ready-to-eat meals from the supermarket freezer—bears the brunt of the blame. This “ultraprocessed” food, he and a growing number of other scientists think, disrupts gut-brain signals that normally tell us that we have had enough, and this failed signaling leads to overeating.

*  *  *

At the end of the 19th century, most Americans lived in rural areas, and nearly half made their living on farms, where fresh or only lightly processed food was the norm. Today most Americans live in cities and buy rather than grow their food, increasingly in ready-to-eat form. An estimated 58 percent of the calories we consume and nearly 90 percent of all added sugars come from industrial food formulations made up mostly or entirely of ingredients—whether nutrients, fiber or chemical additives—that are not found in a similar form and combination in nature. These are the ultraprocessed foods, and they range from junk food such as chips, sugary breakfast cereals, candy, soda and mass-manufactured pastries to what might seem like benign or even healthful products such as commercial breads, processed meats, flavored yogurts and energy bars.

Wasn’t David Kessler, M.D., saying the same things ten years ago?

Here’s another new theory from me: If you had to kill and butcher your own animals, you’d eat less.

Steve Parker, M.D.

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Were Early Homo Carnivorous?: The feeding behavior of early Homo at Olduvai Gorge, Tanzania

From the Journal of Human Evolution:


The regular consumption of large mammal carcasses, as evidenced by butchery marks on fossils recovered from Early Stone Age archaeological sites, roughly coincides with the appearance of Homo habilis. However, the significance of this niche expansion cannot be appreciated without an understanding of hominin feeding behavior and their ecological interactions with mammalian carnivores. The Olduvai Geochronology and Archaeology Project (OGAP) has recovered a large and well-preserved fossil assemblage from the HWK EE site, which was deposited just prior to the first appearance of Acheulean technology at Olduvai Gorge and likely represents one of the last H. habilis sites at Olduvai. This taphonomic analysis of the larger mammal fossil assemblage excavated from HWK EE shows evidence of multiple occupations over a long period of time, suggesting the site offered resources that were attractive to hominins. There was a water source indicated by the presence of fish, crocodiles, and hippos, and there was possible tree cover in an otherwise open habitat. The site preserves several stratigraphic intervals with large fossil and artifact assemblages within two of these intervals. Feeding traces on bone surfaces suggest hominins at the site obtained substantial amounts of flesh and marrow, particularly from smaller size group 1-2 carcasses, and exploited a wide range of taxa, including megafauna. A strong carnivore signal suggests hominins scavenged much of their animal foods during the two main stratigraphic intervals. In the later interval, lower carnivore tooth mark and hammerstone percussion mark frequencies, in addition to high epiphyseal to shaft fragment ratios, suggest hominins and carnivores did not fully exploit bone marrow and grease, which may have been acquired from nutritionally-stressed animals that died during a dry period at Olduvai. The diversity of fauna that preserve evidence of butchery suggests that the HWK EE hominins were opportunistic in their acquisition of carcass foods.

Source: The carnivorous feeding behavior of early Homo at HWK EE, Bed II, Olduvai Gorge, Tanzania. – PubMed – NCBI

Steve Parker, M.D.

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Gut microbiome response to a modern Paleolithic diet

From PloS One:


The modern Paleolithic diet (MPD), featured by the consumption of vegetables, fruit, nuts, seeds, eggs, fish and lean meat, while excluding grains, dairy products, salt and refined sugar, has gained substantial public attention in recent years because of its potential multiple health benefits. However, to date little is known about the actual impact of this dietary pattern on the gut microbiome (GM) and its implications for human health. In the current scenario where Western diets, low in fiber while rich in industrialized and processed foods, are considered one of the leading causes of maladaptive GM changes along human evolution, likely contributing to the increasing incidence of chronic non-communicable diseases, we hypothesize that the MPD could modulate the Western GM towards a more “ancestral” configuration. In an attempt to shed light on this, here we profiled the GM structure of urban Italian subjects adhering to the MPD, and compared data with other urban Italians following a Mediterranean Diet (MD), as well as worldwide traditional hunter-gatherer populations from previous publications. Notwithstanding a strong geography effect on the GM structure, our results show an unexpectedly high degree of biodiversity in MPD subjects, which well approximates that of traditional populations. The GM of MPD individuals also shows some peculiarities, including a high relative abundance of bile-tolerant and fat-loving microorganisms. The consumption of plant-based foods-albeit with the exclusion of grains and pulses-along with the minimization of the intake of processed foods, both hallmarks of the MPD, could therefore contribute to partially rewild the GM but caution should be taken in adhering to this dietary pattern in the long term.

Source: Gut microbiome response to a modern Paleolithic diet in a Western lifestyle context. – PubMed – NCBI

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Effects of a Paleolithic Diet on Cardiovascular Disease Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. – PubMed – NCBI

I’ve probably read and blogged here about most of the individual articles that comprise this meta-analysis.

Effects of a Paleolithic Diet on Cardiovascular Disease Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.


There is some evidence supporting the beneficial effects of a Paleolithic Diet (PD) on cardiovascular disease risk factors. This diet advises consuming lean meat, fish, vegetables, fruits, and nuts and avoiding intake of grains, dairy products, processed foods, and added sugar and salt. This study was performed to assess the effects of a PD on cardiovascular disease risk factors including anthropometric indexes, lipid profile, blood pressure, and inflammatory markers using data from randomized controlled trials. A comprehensive search was performed in the PubMed, Scopus, ISI Web of Science, and Google Scholar databases up to August, 2018. A meta-analysis was performed using a random-effects model to estimate the pooled effect size. Meta-analysis of 8 eligible studies revealed that a PD significantly reduced body weight [weighted mean difference (WMD) = -2.17 kg; 95% CI: -3.48, -0.87 kg], waist circumference (WMD = -2.90 cm; 95% CI: -4.51, -1.28 cm), body mass index (in kg/m2) (WMD = -1.15; 95% CI: -1.68, -0.62), body fat percentage (WMD = -1.38%; 95% CI: -2.08%, -0.67%), systolic (WMD = -4.24 mm Hg; 95% CI: -7.11, -1.38 mm Hg) and diastolic (WMD = -2.95 mm Hg; 95% CI: -4.72, -1.18 mm Hg) blood pressure, and circulating concentrations of total cholesterol (WMD = -0.22 mg/dL; 95% CI: -0.42, -0.03 mg/dL), TGs (WMD = -0.23 mg/dL; 95% CI: -0.46, -0.01 mg/dL), LDL cholesterol (WMD = -0.13 mg/dL; 95% CI: -0.25, -0.01 mg/dL), and C-reactive protein (CRP) (WMD = -0.41 mg/L; 95% CI: -0.81, -0.008 mg/L) and also significantly increased HDL cholesterol (WMD = 0.05 mg/dL; 95% CI: 0.005, 0.10 mg/dL). However, sensitivity analysis revealed that the overall effects of a PD on lipid profile, blood pressure, and circulating CRP concentrations were significantly influenced by removing some studies, hence the results must be interpreted with caution. Although the present meta-analysis revealed that a PD has favorable effects on cardiovascular disease risk factors, the evidence is not conclusive and more well-designed trials are still needed.

Advances in Nutrition. 2019 Apr 30. pii: nmz007. doi: 10.1093/advances/nmz007. [Epub ahead of print]. Authors are Ghaedi E., Mohammadi M, Mohammadi H, Ramezani-Jolfaie N, Malekzadeh J, Hosseinzadeh M, Salehi-Abargouei A.

Source: Effects of a Paleolithic Diet on Cardiovascular Disease Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. – PubMed – NCBI

For the  Multiple Sclerosis Community: Compare Low Saturated Fat and Modified Paleolithic Diets

Wahls or Low Saturated Fat? He needs the calories from fat.


The precise etiology of multiple sclerosis (MS) is unknown but epidemiologic evidence suggests this immune-mediated, neurodegenerative condition is the result of a complex interaction between genes and lifetime environmental exposures. Diet choices are modifiable environmental factors that may influence MS disease activity. Two diets promoted for MS, low saturated fat Swank and modified Paleolithic Wahls Elimination (WahlsElim), are currently being investigated for their effect on MS-related fatigue and quality of life (NCT02914964). Dr. Swank theorized restriction of saturated fat would reduce vascular dysfunction in the central nervous system (CNS). Dr. Wahls initially theorized that detailed guidance to increase intake of specific foodstuffs would facilitate increased intake of nutrients key to neuronal health (Wahls™ diet). Dr. Wahls further theorized restriction of lectins would reduce intestinal permeability and CNS inflammation (WahlsElim version). The purpose of this paper is to review the published research of the low saturated fat (Swank) and the modified Paleolithic (Wahls™) diets and the rationale for the structure of the Swank diet and low lectin version of the Wahls™ diet (WahlsElim) being investigated in the clinical trial.”

Source: Review of Two Popular Eating Plans within the Multiple Sclerosis Community: Low Saturated Fat and Modified Paleolithic. – PubMed – NCBI

What Fruits And Vegetables Looked Like Before We Domesticated Them

paleo diet, paleo meal, recipe, stone age diet, paleo food, hunter-gatherer food

One of the paleo meals I took to the hospital to eat mid-shift

From Science Alert:

While GMOs may involve splicing genes from other organisms (such as bacteria) to give plants desired traits – like resistance to pests — selective breeding is a slower process whereby farmers select and grow crops with those traits over time.

From bananas to eggplant, here are some of the foods that looked totally different before humans first started growing them for food.

Source: Here’s What Fruits And Vegetables Looked Like Before We Domesticated Them

Jane Brody Asks: Is the Paleo Diet Right for You?

Not your average cave-woman

Jane Brody at the New York Times wrote an article critical of the paleo diet. One of her objections is that average life spans in the pre-agricultural era were hardly longer than 40 years, so we have no idea what effect the paleo diet would have on longevity and prevention of late-onset “diseases of civilization.”

She writes:

Keep in mind that the life expectancy of people before the advent of agriculture 15,000 years ago rarely reached or exceeded 40, so their risk of developing the so-called diseases of civilization is unknown.

First of all, the widespread adoption of agriculture is thought to have occurred 10-12,000 years ago, not 15,000 years.

Secondly, even in 1900 average life span in the U.S. was only 47 years.

But read her entire article for yourself. She didn’t change my mind.

Steve Parker, M.D.


Paleo Theory: The sedentary (r)evolution: Have we lost our metabolic flexibility?


If you can’t easily go over four hours without eating something, you’ve lost your metabolic flexibility. Or something.

European authors in F1000Research (?!) suggest we consider our hunter-gatherer roots for clues to prevention of diseases of modern civilization. Here’s the abstract to whet your appetite:

During the course of evolution, up until the agricultural revolution, environmental fluctuations forced the human species to develop a flexible metabolism in order to adapt its energy needs to various climate, seasonal and vegetation conditions. Metabolic flexibility safeguarded human survival independent of food availability. In modern times, humans switched their primal lifestyle towards a constant availability of energy-dense, yet often nutrient-deficient, foods, persistent psycho-emotional stressors and a lack of exercise. As a result, humans progressively gain metabolic disorders, such as the metabolic syndrome, type 2 diabetes, non-alcoholic fatty liver disease, certain types of cancer, cardiovascular disease and Alzheimer´s disease, wherever the sedentary lifestyle spreads in the world. For more than 2.5 million years, our capability to store fat for times of food shortage was an outstanding survival advantage. Nowadays, the same survival strategy in a completely altered surrounding is responsible for a constant accumulation of body fat. In this article, we argue that the metabolic disease epidemic is largely based on a deficit in metabolic flexibility. We hypothesize that the modern energetic inflexibility, typically displayed by symptoms of neuroglycopenia, can be reversed by re-cultivating suppressed metabolic programs, which became obsolete in an affluent environment, particularly the ability to easily switch to ketone body and fat oxidation. In a simplified model, the basic metabolic programs of humans’ primal hunter-gatherer lifestyle are opposed to the current sedentary lifestyle. Those metabolic programs, which are chronically neglected in modern surroundings, are identified and conclusions for the prevention of chronic metabolic diseases are drawn.

Source: The sedentary (r)evolution: Have we lost our metabolic flexibility?

Paleo and Mediterranean Diets Linked to Lower Risk of Death

The Journal of Nutrition in 2017 published a study that looked at baseline diet characteristics of over 21,000 folks, then over the next six years noted who died, and why. Guess how many died?

Here’s a clue. These U.S. study participants were at least 45 years old at the start of the study.

2,513 died. Seems high to me, so I bet the average age was close to 65.

Hank’s not worried about death

I can’t tell for sure from the report’s abstract, but it looks like the researchers were interested in the Mediterranean and caveman diets from the get-go. Study subjects who ate Paleo- or Mediterranean-style were significantly less likely to die over six years. They were less likely to die from any cause or from cancer or from cardiovascular disease.

Composition of the paleo diet is debatable (click for my 2012 definition).

Consider adopting some Mediterranean diet features, too.

Steve Parker, M.D.


Paleolithic and Mediterranean Diet Pattern Scores Are Inversely Associated with All-Cause and Cause-Specific Mortality in Adults. First published February 8, 2017, doi: 10.3945/​jn.116.241919.


Background: Poor diet quality is associated with a higher risk of many chronic diseases that are among the leading causes of death in the United States. It has been hypothesized that evolutionary discordance may account for some of the higher incidence and mortality from these diseases.

Objective: We investigated associations of 2 diet pattern scores, the Paleolithic and the Mediterranean, with all-cause and cause-specific mortality in the REGARDS (REasons for Geographic and Racial Differences in Stroke) study, a longitudinal cohort of black and white men and women ≥45 y of age.

Methods: Participants completed questionnaires, including a Block food-frequency questionnaire (FFQ), at baseline and were contacted every 6 mo to determine their health status. Of the analytic cohort (n = 21,423), a total of 2513 participants died during a median follow-up of 6.25 y. We created diet scores from FFQ responses and assessed their associations with mortality using multivariable Cox proportional hazards regression models adjusting for major risk factors.

Results: For those in the highest relative to the lowest quintiles of the Paleolithic and Mediterranean diet scores, the multivariable adjusted HRs for all-cause mortality were, respectively, 0.77 (95% CI: 0.67, 0.89; P-trend < 0.01) and 0.63 (95% CI: 0.54, 0.73; P-trend < 0.01). The corresponding HRs for all-cancer mortality were 0.72 (95% CI: 0.55, 0.95; P-trend = 0.03) and 0.64 (95% CI: 0.48, 0.84; P-trend = 0.01), and for all-cardiovascular disease mortality they were 0.78 (95% CI: 0.61, 1.00; P-trend = 0.06) and HR: 0.68 (95% CI: 0.53, 0.88; P-trend = 0.01).

Conclusions: Findings from this biracial prospective study suggest that diets closer to Paleolithic or Mediterranean diet patterns may be inversely associated with all-cause and cause-specific mortality.


Who Said the Paleo Diet Cures Dementia?

Christopher E. Pitt, a general practitioner in Australia, wrote an article in 2016 questioning the safety of the paleo diet and veracity of some of its more prominent advocates. Dr. Pitt reviewed most of the available scientific studies and concluded:

Overall, conclusions about the effectiveness of the Palaeolithic diet should be considered cautiously. Positive findings should be tempered by the lack of power of these studies, which were limited by their small numbers, heterogeneity and short duration. Nevertheless, there appears to be enough evidence to warrant further consideration of the Palaeolithic diet as a potential dietary option in the management of metabolic diseases. Larger independent trials with consistent methodology and longer duration are required to confirm the initial promise in these early studies. Claims that the Palaeolithic diet could treat or prevent conditions such as autism, dementia and mental illness are not supported by clinical research.

The Palaeolithic diet is currently over-hyped and under-researched. While the claims made by its celebrity proponents are not supported by current evidence, the Palaeolithic diet may be of benefit in the management of various metabolic derangements. Further research is warranted to test these early findings. GPs should caution patients on the Palaeolithic diet about adequate calcium intake, especially those at higher risk of osteoporosis.

I’ve read most of the clinical studies cited by Dr. Pitt and reviewed them here, except I don’t recall the Bligh study. [Bligh HF, Godsland IF, Frost G, et al. Plant-rich mixed meals based on Palaeolithic diet principles have a dramatic impact on incretin, peptide YY and satiety response, but show little effect on glucose and insulin homeostasis: An acute-effects randomised study. Br J Nutr 2015;113:574–84.]

I’m not going to address Dr. Pitt’s article point by point. I merely bring it to your attention for your consideration. I will say I think Dr. Pitt is being too deferential to entrenched and sclerotic “authoritative” panels (e.g., Australian dietary guidelines). I was the same until 2009. Regarding calcium, you’ll find my assessment via the search box above and to the right.

I certainly agree with Dr. Pitt that the paleo diet is no panacea, and that further research is warranted.

Steve Parker, M.D.