Thursday, August 25, 2011

A Roadmap to Obesity

In this post, I'll explain my current understanding of the factors that promote obesity in humans.  


To a large degree, obesity is a heritable condition.  Various studies indicate that roughly two-thirds of the differences in body fatness between individuals is explained by heredity*, although estimates vary greatly (1).  However, we also know that obesity is not genetically determined, because in the US, the obesity rate has more than doubled in the last 30 years, consistent with what has happened to many other cultures (2).  How do we reconcile these two facts?  By understanding that genetic variability determines the degree of susceptibility to obesity-promoting factors.  In other words, in a natural environment with a natural diet, nearly everyone would be relatively lean, but when obesity-promoting factors are introduced, genetic makeup determines how resistant each person will be to fat gain.  As with the diseases of civilization, obesity is caused by a mismatch between our genetic heritage and our current environment.  This idea received experimental support from an interesting recent study (3).

Sunday, August 21, 2011

Seed Oils and Body Fatness-- A Problematic Revisit

Anthony Colpo recently posted a discussion of one of my older posts on seed oils and body fat gain (1), which reminded me that I need to revisit the idea.  As my knowledge of obesity and metabolism has expanded, I feel the evidence behind the hypothesis that seed oils (corn, soybean, etc.) promote obesity due to their linoleic acid (omega-6 fat) content has largely collapsed.

Thursday, August 18, 2011

Food Palatability and Body Fatness: Clues from Alliesthesia

Part I: Is there a Ponderostat?

Some of the most important experiments for understanding the role of food palatability/reward in body fatness were performed by Dr. Michel Cabanac and collaborators in the 1970s (hat tip to Dr. Seth Roberts for the references).  In my recent food reward series (1), I referenced but did not discuss Dr. Cabanac's work because I felt it would have taken too long to describe.  However, I included two of his studies in my Ancestral Health Symposium talk, and I think they're worth discussing in more detail here.

Monday, August 15, 2011

I Got Boinged, and Other News

The reaction to my post "The Carbohydrate Hypothesis of Obesity: a Critical Examination" has been overwhelmingly positive, particularly among the scientists I've heard from. 

On Saturday, the inimitable maker and writer Mark Frauenfelder posted a link to my post on the variety blog BoingBoing.  BoingBoing has been on my sidebar for three years, and it's the place I go when I need a break.  It's a fun assortment of science, news, technology and entertainment.  BoingBoing was originally a zine started by Frauenfelder and his wife in 1988, and it has been on the web since 1995.  Today, it has multiple contributing authors and it draws several hundred thousand hits per day.  I'm thrilled that Frauenfelder posted my article there.  Apparently he likes my blog.  Thanks!

I added a new section (IIB) to my original post.  It discusses what human genetics can teach us about the mechanisms of common obesity.  It is consistent with the rest of the evidence suggesting that body fatness is primarily regulated by the brain, not by fat tissue, and that leptin signaling plays a dominant role in this process. 

Thursday, August 11, 2011

The Carbohydrate Hypothesis of Obesity: a Critical Examination


I'd like to begin by emphasizing that carbohydrate restriction has helped many people lose body fat and improve their metabolic health.  Although it doesn't work for everyone, there is no doubt that carbohydrate restriction causes fat loss in many, perhaps even most obese people.  For a subset of people, the results can be very impressive.  I consider that to be a fact at this point, but that's not what I'll be discussing here. 

What I want to discuss is a hypothesis.  It's the idea, championed by Gary Taubes, that carbohydrate (particularly refined carbohydrate) is the primary cause of common obesity due to its ability to elevate insulin, thereby causing increased fat storage in fat cells.  To demonstrate that I'm representing this hypothesis accurately, here is a quote from his book Good Calories, Bad Calories:

Monday, August 8, 2011

Ancestral Health Symposium

Last weekend I attended the Ancestral Health Symposium at the University of California, Los Angeles, organized by Aaron Blaisdell, Brent Pottenger and Seth Roberts with help from many others.  It was a really great experience and I'm grateful to have been invited.  I was finally able to meet many of the people who I respect and admire, but knew only through the internet.  I'm not going to make a list because it would be too long, but if you take a look at the symposium schedule, I think you'll understand where I'm coming from.  I was also able to connect with a number of Whole Health Source readers, which was great.  I recognized some of them from the comments section.  Now I know it wasn't just my mom with 57 Google accounts.

The symposium was the first of its kind, and represented many facets of the ancestral health community, including "Paleolithic" diet and exercise patterns, low-carbohydrate diets, Weston Price-style diets, traditional health-nutrition researchers as well as other camps.  For the most part they coexisted peacefully and perhaps even learned a thing or two from one another. 

I was very impressed by the appearance of the attendees.  Young men and women were fit with glowing skin, and older attendees were energetic and aging gracefully.  It would be hard to come up with a better advertisement for ancestrally-oriented diets and lifestyles.  I saw a lot of people taking the stairs rather than the elevator.  I like to say I'll take the elevator/escalator when I'm dead.  I think integrating exercise into everyday life is healthy and efficient.  Escalators and elevators of course make sense for people with physical disabilities or heavy suitcases.

The first talk was by Dr. Boyd Eaton, considered by many to be the grandfather of the paleolithic diet concept.  I was very impressed by his composure, humility and compassionate attitude.  Half his talk was dedicated to environmental and social problems.  Dr. Staffan Lindeberg gave a talk titled "Food and Western Disease", which covered his paleolithic diet clinical trials as well as other evidence supporting ancestral diets.  I like Dr. Lindeberg's humble and skeptical style of reasoning.  I had the great pleasure of having dinner with Dr. Lindeberg and his wife, Dr. Eaton, Pedro Bastos, Dr. Lynda Frassetto, Dr. Guy-Andre Pelouze and his son Alexandre.  Pedro gave a very nice talk on the complexities of traditional and modern dairy.  The following night, I was able to connect with other writers I enjoy, including Chris Masterjohn, Melissa McEwen, John Durant, and Denise Minger

Dr. Pelouze is a french cardiovascular surgeon who strongly supports the food reward/palatability concept of obesity.  We had a conversation the evening before the conference, during which he basically made the same points I was going to make in my talk.  He is particularly familiar with the research of Dr. Michel Cabanac, who is central to the food reward idea.  He eats an interesting diet: mostly raw, omnivorous, and extremely simple.  If I understood correctly, he mostly eats raw meat, fish, fruit and vegetables with little or no preparation.  He sometimes cooks food if he wants to, but most of it is raw.  He believes simple, raw food allows the body's satiety systems to work more effectively.  He has been eating this way for more than twenty years, and his son was raised this way and is now about my age (if I recall correctly, Alexandre has a masters and is studying for an MD, and ultimately wants to become an MD/PhD).  Both of them look very good, are full of energy and have a remarkably positive mental state.  Alexandre told me that he never felt deprived growing up around other children who ate pastries, candy et cetera.  They woke up early and ran six miles before the conference began at 8 am. 

I gave my talk on Friday.  Giving a talk is not like writing a blog post-- it has to be much more cohesive and visually compelling.  I put a lot of work into it and it went really well.  Besides the heat I got from from Gary Taubes in the question and answer session, the response was very positive.  The talk, including the questions, will be freely available on the internet soon, as well as other talks from the symposium.  Some of it will be familiar to people who have read my body fat setpoint and food reward series, but it's a concise summary of the ideas and parts of it are new, so it will definitely be worthwhile to watch it.  

We have entered a new era of media communication.  Every time someone sneezed, it was live tweeted.  There are some good aspects to it-- it democratizes information by making it more accessible.  On the other hand, it's sometimes low quality information that contains inaccurate accounts and quotes that are subsequently recirculated. 

It was a great conference and I hope it was the first of many.