Media Appearances

Last October, I participated in a panel discussion organized by the Harvard Food Law Society in Boston.  The panel included Drs. Walter Willett, David Ludwig, Robert Lustig, and myself, with Corby Kummer as moderator.  Dr. Willett is the chair of the Harvard Department of Nutrition; Dr. Ludwig is a professor of nutrition and pediatrics at Harvard; Dr. Lustig is a professor of clinical pediatrics at UCSF; and Kummer is a food writer and senior editor for The Atlantic. 
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Exercise and Food Intake

The New York Times just published an article reviewing some of the recent research on exercise, food intake and food reward, titled "Does Exercise Make You Overeat?".  I was planning to write about this at some point, but I don't know when I'd be able to get around to it, and the NYT article is a fair treatment of the subject, so I'll just point you to the article.

Basically, burning calories through exercise causes some people to eat more, but not everyone does, and a few people actually eat less.  Alex Hutchinson discussed this point recently on his blog (1).  Part of it depends on how much fat you carry-- if you're already lean, the body is more likely to increase hunger because it very much dislikes going too low in body fat.  Most overweight/obese people do not totally make up for the calories they burn through exercise by eating more, so they lose fat.  There is a lot of individual variability here.  The average obese person won't lose a substantial amount of fat through exercise alone.  However, everyone knows someone who lost 50+ pounds through exercise alone, and the controlled trials support that it happens in a minority of people.  On the other side of the spectrum, I have a friend who gained fat while training for a marathon, and lost it afterward. 

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Recent Media Appearances

Men's Health interviewed and quoted me in an article titled "Reprogram Your Metabolism", written by Lou Schuler.  Part of the article was related to the food reward concept.  I'm glad to see the idea gradually reaching the mainstream. 

Boing Boing recently covered an article by Dr. Hisham Ziauddeen and colleagues in Nature Reviews Neuroscience that questioned the idea that common obesity represents food addiction-- an idea that I often encounter in my reading.  Maggie Koerth-Baker asked me if I wanted to respond.  I sent her a response explaining that I agree with the authors' conclusions and I also doubt obesity is food addiction per se, as I have explained in the past, although a subset of obese people can be addicted to food.  I explained that the conclusions of the paper are consistent with the idea that food reward influences fat mass.  You can find my explanation here.

Food Reward: Approaching a Scientific Consensus

Review papers provide a bird's-eye view of a field from the perspective of experts.  Recent review papers show that many obesity researchers are converging on a model for the development of obesity that includes excessive food reward*, in addition to other factors such as physical inactivity, behavioral traits, and alterations in the function of the hypothalamus (a key brain region for the regulation of body fatness).  Take for example the four new review papers I posted recently by obesity and reward researchers:
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Qnexa, the Latest Obesity Drug

There are very few obesity drugs currently approved for use in the US-- not because effective drugs don't exist, but because the FDA has judged that the side effects of existing drugs are unacceptable. 

Although ultimately I believe the most satisfying resolution to the obesity epidemic will not come from drugs, drugs offer us a window intn the biological processes that underlie obesity and fat loss.  Along those lines, here's a quote from a review paper on obesity drugs that I think is particularly enlightening (1):
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Boing!

I just had a featured article published on Boing Boing, "Seduced by Food: Obesity and the Human Brain".  Boing Boing is the most popular blog on the Internet, with over 5 million unique visitors per month, and it's also one of my favorite haunts, so it was really exciting for me to be invited to submit an article.  For comparison, Whole Health Source had about 72,000 unique visitors last month (200,000+ hits).

The article is a concise review of the food reward concept, and how it relates to the current obesity epidemic.  Concise compared to all the writing I've done on this blog, anyway.  I put a lot of work into making the article cohesive and understandable for a somewhat general audience, and I think it's much more effective at explaining the concept than the scattered blog posts I've published here.  I hope it will clear up some of the confusion about food reward.  I don't know what's up with the image they decided to use at the top. 

Many thanks to Mark Frauenfelder, Maggie Koerth-Baker, and Rob Beschizza for the opportunity to publish on Boing Boing, as well as their comments on the draft versions!

For those who have arrived at Whole Health Source for the first time via Boing Boing, welcome!   Have a look around.  The "labels" menu on the sidebar is a good place to start-- you can browse by topic.

Palatability, Satiety and Calorie Intake

WHS reader Paul Hagerty recently sent me a very interesting paper titled "A Satiety Index of Common Foods", by Dr. SHA Holt and colleagues (1).  This paper quantified how full we feel after eating specific foods.  I've been aware of it for a while, but hadn't read it until recently.  They fed volunteers a variety of commonly eaten foods, each in a 240 calorie portion, and measured how full each food made them feel, and how much they ate at a subsequent meal.  Using the results, they calculated a "satiety index", which represents the fullness per calorie of each food, normalized to white bread (white bread arbitrarily set to SI = 100).  So for example, popcorn has a satiety index of 154, meaning it's more filling than white bread per calorie. 

One of the most interesting aspects of the paper is that the investigators measured a variety of food properties (energy density, fat, starch, sugar, fiber, water content, palatability), and then determined which of them explained the SI values most completely.

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Is Sugar Fattening?

Buckle your seat belts, ladies and gentlemen-- we're going on a long ride through the scientific literature on sugar and body fatness.  Some of the evidence will be surprising and challenging for many of you, as it was for me, but ultimately it paints a coherent and actionable picture.

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What Causes Insulin Resistance? Part VII

In previous posts, I outlined the factors I'm aware of that can contribute to insulin resistance.  In this post, first I'll list the factors, then I'll provide my opinion of effective strategies for preventing and potentially reversing insulin resistance.

The factors

These are the factors I'm aware of that can contribute to insulin resistance, listed in approximate order of importance.  I could be quite wrong about the order-- this is just my best guess. Many of these factors are intertwined with one another. 
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New Obesity Review Paper by Yours Truly

The Journal of Clinical Endocrinology and Metabolism just published a clinical review paper written by myself and my mentor Dr. Mike Schwartz, titled "Regulation of Food Intake, Energy Balance, and Body Fat Mass: Implications for the Pathogenesis and Treatment of Obesity" (1).  JCEM is one of the most cited peer-reviewed journals in the fields of endocrinology, obesity and diabetes, and I'm very pleased that it spans the gap between scientists and physicians.  Our paper takes a fresh and up-to-date look at the mechanisms by which food intake and body fat mass are regulated by the body, and how these mechanisms are altered in obesity.  We explain the obesity epidemic in terms of the mismatch between our genes and our current environment, a theme that is frequently invoked in ancestral health circles.

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60 Minutes Report on the Flavorist Industry

A reader sent me a link to a recent CBS documentary titled "Tweaking Tastes and Creating Cravings", reported by Morley Safer.

Safer describes the "flavorist" industry, entirely dedicated to crafting irresistible odors for the purpose of selling processed and restaurant food.  They focused on the company Givaudin.  Dr. David Kessler, author of The End of Overeating, makes an appearance near the end.

Here are a few notable quotes:

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New Review Papers on Food Reward

As research on the role of reward/palatability in obesity continues to accelerate, interesting new papers are appearing weekly.  Here is a roundup of review papers I've encountered in the last three months.  These range from somewhat technical to very technical, but I think they should be mostly accessible to people with a background in the biological sciences. 

Food and Drug Reward: Overlapping Circuits in Human Obesity and Addiction
Written by Dr. Nora D. Volkow and colleagues.  This paper describes the similarities between the mechanisms of obesity and addiction, with a focus on human brain imaging studies.  Most researchers don't think obesity is an addiction per se, but the mechanisms (e.g., brain areas important for reward) do seem to overlap considerably.  This paper is well composed and got a lot of media attention.  Dr. Volkow is the director of the National Institute on Drug Abuse, a branch of the National Institutes of Health.  The NIH is the main source of biomedical research funding in the US, and also conducts its own research.

Here's a quote from the paper:

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Another Simple Food Weight Loss Experience

Whole Health Source reader Sarah Pugh recently went on a six-week simple food (low reward) diet to test its effectiveness as a weight loss strategy, and she was kind enough to describe her experience for me, and provide a link to her blog where she discussed it in more detail (1). 

Consistent with the scientific literature and a number of previous reader anecdotes (2), Sarah experienced a reduction in appetite on the simple food diet, losing 15 pounds in 6 weeks without hunger.  In contrast to her prior experiences with typical calorie restriction, her energy level and mood remained high over this period.  Here's a quote from her blog:

Well, it looks like the theory that in the absence of nice palatable food, the body will turn quite readily to fat stores and start munching them up, is holding up. At the moment, the majority of the energy I use is coming from my insides, and my body is using it without such quibbles as the increased hunger, low energy, crappy thermo-regulation or bitchiness normally associated with severe calorie restriction.

I can't promise that everyone will experience results like this, but this is basically what the food reward hypothesis suggests should be possible, and it seems to work this way for many people.  That's one of the reasons why this idea interests me so much.

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This post was written by Stephan Guyenet for Whole Health Source.

A Brief Response to Taubes's Food Reward Critique, and a Little Something Extra

It appears Gary Taubes has completed his series critiquing the food reward hypothesis of obesity (1).  I have to hand it to him, it takes some cojones to critique an entire field of research, particularly when you have no scientific background in it.

The food reward hypothesis of obesity states that the reward and palatability value of food influence body fatness, and excess reward/palatability can promote body fat accumulation.  If we want to test the hypothesis, the most direct way is to find experiments in which 1) the nutritional qualities of the experimental diet groups are kept the same or at least very similar, 2) some aspect of diet reward/palatability differs, and 3) changes in body fat/weight are measured (for example, 2, 3, 4, 5, 6, 7, 8, 9).  In these experiments the hypothesis has both arms and one leg tied behind its back, because the most potent reward factors (energy density, sugar, fat) have nutritional value and therefore experiments that modify these cannot be tightly controlled for nutritional differences.  Yet even with this severe disadvantage, the hypothesis is consistently supported by the scientific evidence.  Taubes repeatedly stated in his series that controlled studies like these have not been conducted, apparently basing this belief on a 22-year-old review paper by Dr. Israel Ramirez and colleagues that does not contain the word 'reward' (10).

Another way to test the hypothesis is to see if people with higher food reward sensitivity (due to genetics or other factors) tend to gain more fat over time (for example, 11, 12, 13, 14, 15, 16).  In addition, studies that have examined the effect of palatability/reward on food intake in a controlled manner are relevant (17, 18, 19, 20, 21, 22), as are studies that have identified some of the mechanisms by which these effects occur (reviewed in 23).  Even if not all of the studies are perfect, at some point, one has to acknowledge that there are a lot of mutually buttressing lines of evidence here.  It is notable that virtually none of these studies appeared in Taubes's posts, and he appeared largely unaware of them. 
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Losing Fat With Simple Food-- Two Reader Anecdotes

Each week, I'm receiving more e-mails and comments from people who are successfully losing fat by eating simple (low reward) food, similar to what I described here.  In some cases, people are breaking through fat loss plateaus that they had reached on conventional low-carbohydrate, low-fat or paleo diets.  This concept can be applied to any type of diet, and I believe it is an important characteristic of ancestral food patterns.

At the Ancestral Health Symposium, I met two Whole Health Source readers, Aravind Balasubramanian and Kamal Patel, who were interested in trying a simple diet to lose fat and improve their health.  In addition, they wanted to break free of certain other high-reward activities in their lives that they felt were not constructive.  They recently embarked on an 8-week low-reward diet and lifestyle to test the effectiveness of the concepts.  Both of them had previously achieved a stable (in Aravind's case, reduced) weight on a paleo-ish diet prior to this experiment, but they still carried more fat than they wanted to.  They offered to write about their experience for WHS, and I thought other readers might find it informative.  Their story is below, followed by a few of my comments.

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The Case for the Food Reward Hypothesis of Obesity, Part HI

In this post, I'll explore whether or not the scientific evidence is consistent with the predictions of the food reward hypothesis, as outlined in the last post.

Before diving in, I'd like to address the critique that the food reward concept is a tautology or relies on circular reasoning (or is not testable/falsifiable).  This critique has no logical basis.  The reward and palatability value of a food is not defined by its effect on energy intake or body fatness.  In the research setting, food reward is measured by the ability of food or food-related stimuli to reinforce or motivate behavior (e.g., 1).  In humans, palatability is measured by having a person taste a food and rate its pleasantness in a standardized, quantifiable manner, or sometimes by looking at brain activity by fMRI or related techniques (2).  In rodents, it is measured by observing stereotyped facial responses to palatable and unpalatable foods, which are similar to those seen in human infants.  It is not a tautology or circular reasoning to say that the reinforcing value or pleasantness of food influences food intake and body fatness. These are quantifiable concepts and as I will explain, their relationship with food intake and body fatness can be, and already has been, tested in a controlled manner. 

1.   Increasing the reward/palatability value of the diet should cause fat gain in animals and humans

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The Case for the Food Reward Hypothesis of Obesity, Part I

Introduction

When you want to investigate something using the scientific method, first you create a model that you hope describes a natural phenomenon-- this is called a hypothesis.  Then you go about testing that model against reality, under controlled conditions, to see if it has any predictive power.  There is rarely a single experiment, or single study, that can demonstrate that a hypothesis is correct.  Most important hypotheses require many mutually buttressing lines of evidence from multiple research groups before they're widely accepted.  Although it's not necessary, understanding the mechanism by which an effect occurs, and having that mechanism be consistent with the hypothesis, adds substantially to the case.

With that in mind, this post will go into greater detail on the evidence supporting food reward and palatability as major factors in the regulation of food intake and body fatness.  There is a large amount of supportive evidence at this point, which is rapidly expanding due to the efforts of many brilliant researchers, however for the sake of clarity and brevity, so far I've only given a "tip of the iceberg" view of it.  But there are two types of people who want more detail: (1) the skeptics, and (2) scientifically inclined people who want mechanism.  This post is for them.  It will get technical at times, as there is no other way to convey the material effectively.

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Humans on a Cafeteria Diet

In the 1970s, as the modern obesity epidemic was just getting started, investigators were searching for new animal models of diet-induced obesity.  They tried all sorts of things, from sugar to various types of fats, but none of them caused obesity as rapidly and reproducibly as desired*.  1976, Anthony Sclafani tried something new, and disarmingly simple, which he called the "supermarket diet": he gave his rats access to a variety of palatable human foods, in addition to standard rodent chow.  They immediately ignored the chow, instead gorging on the palatable food and rapidly becoming obese (1).  Later renamed the "cafeteria diet", it remains the most rapid and effective way of producing dietary obesity and metabolic syndrome in rodents using solid food (2).

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Book Review: The End of Overeating

The End of Overeating was written based on the personal journey of Dr. David A. Kessler (MD) to understand the obesity epidemic, and treat his own obesity in the process.  Kessler was the FDA commissioner under presidents George HW Bush and Bill Clinton.  He is known for his efforts to regulate cigarettes, and his involvement in modernizing Nutrition Facts labels on packaged food.  He was also the dean of Yale medical school for six years-- a very accomplished person. 

Kessler's book focuses on 1) the ability of food with a high palatability/reward value to cause overeating and obesity, 2) the systematic efforts of the food industry to maximize food palatability/reward to increase sales in a competitive market, and 3) what to do about it.  He has not only done a lot of reading on the subject, but has also participated directly in food reward research himself, so he has real credibility.  The End of Overeating is not the usual diet book baloney. 
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A Roadmap to Obesity

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

Heritability

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).

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