Why Are We Fatter Than Our Ancestors? Interview with Dr. Stephan Guyenet

Why do so many of us overeat – even when we know it’s bad for us?

Like many questions in biology, much of the answer to this question lies in evolution. We know that animals have generally evolved to seek and consume convenient, energy-dense foods. All living things require energy to survive and reproduce, and it makes intuitive sense that genes associated with finding and eating lots of easy calories might be favored by natural selection. This instinct is also evident in humans in natural environments. Hunter-gatherers, who live in conditions similar to that of our evolutionary ancestors, gravitate to delicious high-calorie fare, although they don’t find a great deal of it. When they do get something extra tasty and high in energy – like ripe fruit, fresh meat, and honey – they will gorge on it.

Not unlike us. Modern humans are subject to these impulses as well. So what’s different? Our environment has dramatically changed. Rather than getting rare seasonal opportunities to gorge on rich foods, we are now constantly surrounded by such delicacies. We did not evolve with any need to resist these kinds of tasty treats – so perhaps it is unsurprising that we so often fail despite our best intentions.


In this episode of humanOS Radio, I talk once again with Dr. Stephan Guyenet, this time about his new book, The Hungry Brain, which was just released this week.

In his book, Stephan addresses the fundamental question of why we overeat. It’s not necessarily for a lack of education on nutrition. Rather, it is due to evolutionarily-conserved circuitry in the brain, which drives us to overeat for short-term pleasure – even when we know it’s at the expense of our health and well-being. In the show, he explains how these circuits work to regulate energy intake and body fatness.

Much of this is based on physiology and genetic predispositions – but that doesn’t mean you can’t do anything about it. We also discuss things you can do to manage these primal impulses in a fattening world, and make sure that your daily behaviors are in alignment with your health and weight goals.

Do We Need Less Sleep than We Thought? What Hunter-Gatherers Tell Us (Podcast)

We’re getting much less sleep than we used to! Well, at least that’s been the story, but this story has largely been based on self-reported sleep times. If we are getting less sleep than we should, we need to know. One approach to understanding this subject better is to investigate what “natural” sleep looks like. Luckily, we now have more information on this due to a ground-breaking study recently published by Professor Jerry Siegel at UCLA, and colleagues in the journal Current Biology. In his study, he evaluated three societies living in natural conditions (e.g., modern day hunter-gatherers) to examine their sleep behaviors and physiology. He also analyzed external factors like natural light, ambient temperature and the season in which the data was collected. And by doing so, Dr. Siegel appeared to turn the wide-spread belief that we are chronically sleep deprived on its head. At least that seemed to be the emphasis of most news reports that came out describing the study. But to really understand what this data means, we need to discuss the study and interpret the findings with an emphasis to explain the difference between sleep period and sleep time. Along with an article investigating this subject, you can listen to my interview with Dr. Siegel where we discuss the study and his findings.

A meta-analysis of the Paleolithic nutrition pattern; an interview of authors

Just today, the American Journal of Clinical Nutrition – the most prestigious nutrition journal in the world – published a systematic review and meta-analysis of the paleolithic nutrition pattern (the Paleo diet).

The audio interview below is with study authors, Hanno Pijl, M.D., Ph.D., and Ester van Zuurin, M.D., both of Leiden Unversity in the Netherlands. They, along with authors Eric Manheimer and Zbys Fedorowicz, first performed a systematic review of six online publication libraries for all possible qualifying research. From there, they winnowed the list to four studies, pooling together 159 subjects for their analysis, looking for mean differences in primary endpoints related to metabolic syndrome: 1) Waist circumference, 2) Blood pressure, 3) Triglycerides, 4) HDL cholesterol, and 5) Blood sugar concentration. Secondary endpoints included change in body weight, even though some of the studies included in the analysis tried to prevent weight change so that the results would be less confounded by it. Weight loss, while healthy for someone who is overweight, can also improve these endpoints independently, making it harder to know if it is the nutritional properties of the diet or the weight loss that influenced results. We discuss this specifically in the interview, which you can listen to it here in its entirety.

What Your Doctor Isn’t Thinking About (Dragging Medical Professionals Into the Modern Era)

The other day I came across this alarming video of what it’s like to drive in Poland. My first thought after watching the clip was “What’s the Toxoplasmosis gondii infection rate in Poland?” T. gondii is a brain parasite easily acquired from eating undercooked meat, or contact with cats, and is associated with a six-fold increase in traffic accidents (this association has been replicated a number of times, in different countries). Well, I looked it up, and found that the latent infection rate in 2003 was around 41% (at least among pregnant women). That’s quite high — in the U.S. the infection rate is only about 11%.

Is there anything to my hypothesis that terrible driving in Poland is related to the relatively high T. gondii infection rate? Probably not. The accident fatality rate in Poland is relatively high for a modern industrialized country. But France has a very low accident fatality rate, and a much higher rate of T. gondii infection. So while T. gondii might be a contributing factor, it’s probably not the most important variable.

I’m fascinated by latent/chronic biological infections, and how they affect human health and behavior. T. gondii in particular is linked to changes in personality, and even schizophrenia.