Why Do We Eat? A Neurobiological Perspective. Part I

As with all voluntary movements, eating food is an expression of activity in the brain.  The brain integrates various inputs from around the body, and outside the body, and decides whether or not to execute the goal-directed behaviors of food seeking and consumption.  Research has uncovered a lot about how this process works, and in this series I'll give a simplified overview of what scientists have learned about how, and why, the brain decides to eat.

The Gatekeeper of Voluntary Behaviors

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More Thoughts on Macronutrient Trends

I had a brief positive exchange with Gary Taubes about the NuSI post.  He reminded me that there's an artifact (measurement error) in the USDA data on fat consumption in the year 2000 when they changed assessment methods.  Here are the USDA data on macronutrient consumption since 1970, corrected for loss (28.8%) but not corrected for the artifact:

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Nutrition Science Initiative (NuSI)

Some of you may have heard of an ambitious new nutrition research foundation called the Nutrition Science Initiative (NuSI).  In this post, I'll explain what it is, why it matters, and how I feel about it-- from the perspective of an obesity researcher. 

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Calories and Carbohydrate: a Natural Experiment

In the lab, we work hard to design experiments that help us understand the natural world.  But sometimes, nature sets up experiments for us, and all we have to do is collect the data.  These are called "natural experiments", and they have led to profound insights in every field of science.  For example, Alzheimer's disease is usually not considered a genetic disorder.  However, researchers have identified rare cases where AD is inherited in a simple genetic manner.  By identifying the genes involved, and what they do, we were able to increase our understanding of the molecular mechanisms of the disease.

The natural experiment I'll be discussing today began in 1989 with the onset of a major economic crisis in Cuba. This coincided with the loss of the Soviet Union as a trading partner, resulting in a massive economic collapse over the next six years, which gradually recovered by 2000. 

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AHS11 Talk Posted

After a one-year delay, my talk from the 2011 Ancestral Health Symposium is online with slides synched.  The talk is titled "Obesity: Old Solutions for a New Problem", and it's an overview of some of the research linking food reward to food intake and body fatness.  This is the talk that introduced a fundamentally new idea to the ancestral community: not only does the chemical composition of food matter, but also its sensory qualities-- in fact, the sensory qualities of food are among the primary determinants of food intake.  I didn't come up with the idea of course, I simply translated the research for a more general audience and put my own evolutionary spin on it.

The talk would be a bit different if I were to give it today, as my understanding of the subject has expanded, and my speaking skills have improved.  However, the central message remains as true today as it was a year ago.  You can find the talk here.

The slide synching was done by an extremely generous man named Ben Fury.  As you can see in the video, he did an excellent job.  Without Ben, this video would have remained in internet limbo forever.

Below, I've published a message from Ben explaining the interesting work that he does.  Please contact him if you think it's interesting.

A Message from Ben Fury

I was writing a book on health, fitness and diet in 2009 when my house burned down in the Station Fire, along with 165,000 acres of my beloved Angeles National Forest. Since then, I've had a series of people needing help come through my life, that have upgraded and morphed my talents...

Seniors with chronic pain, falls, brittle bones, and stiff shrunken muscles.
Diabetics with out of control blood sugars, going blind, and having limbs lopped off.
Neurologically challenged people with spastic limbs and foggy brains.
Fat, listless, unhappy people with no idea how they got that way, seeing no way out of the darkness.
Each of them needing help in different ways, but all with an underlying theme of what works to help heal our conditions:

•     Remove flour, sugar, beans, and heavily processed oils from our diet. Eat real food.
•     Get strong.
•     Get flexible.
•     Stop ceding health responsibility to outside forces, and take charge of our own wellness.
•     Only use truly evidence based medicine. Don't just pop the latest pill or get the latest surgery all the other people are doing. Be wary of the disease mongers in both the conventional and alternative camps.
•     Find our "happy thoughts." Use the simple restoratives of sleep, play, and reflection, to let go of pain, find inner peace, and let in joy and purposeful outer direction.

The methods to accomplish these goals are varied, and I have both non-profit and for-profit ventures to share them.
Their websites are currently in development.
The for-profit is BenFury.com
The non-profit is PainRelieversUSA.org , whose mission statement is:

To move beyond pain management...
and learn to live pain free.

Feel free to write to me  at: ben [at] benfury dot com

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Ancestral Health Symposium 2012

I recently returned from AHS12 and a little side trip to visit family.  The conference was hosted at Harvard University through the Harvard Food Law Society.  Many thanks to all the organizers who made it happen.  By and large, it went smoothly.

The science as expected ranged from outstanding to mediocre, but I was really encouraged by the presence and enthusiastic participation of a number of quality researchers and clinicians. The basic concept of ancestral health is something almost anyone can get behind: many of our modern health problems are due to a mismatch between the modern environment and what our bodies "expect".  The basic idea is really just common sense, but of course the devil is in the details when you start trying to figure out what exactly our bodies expect, and how best to give it to them.  I think our perspective as a community is moving in the right direction.

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Lorcaserin: the Latest FDA-approved Obesity Drug

The FDA recently approved a new drug called lorcaserin (brand name Belviq) for the treatment of obesity.  Lorcaserin causes an average of 13 lbs (5.8 kg) of weight loss over a year, compared to 5 lbs (2.2 kg) for placebo (1), which is less than the other recently approved drug Qsymia (formerly Qnexa; topiramate/phentermine).

Learning about obesity drugs is always a good opportunity to gain insight into the mechanisms that underlie the development and reversal of obesity.  If you've been following this blog for a while, you already have a pretty good guess what organ this new drug acts on.  Make your guess and read on!

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Two Great Quotes About Obesity (technical)

By Dr. Hans-Rudolf Berthoud, from a recent paper, "The Neurobiology of Food Intake in an Obesogenic Environment" (1).  I came across it because it cites my review paper (2).  My perspective on obesity is similar to his.  From the abstract:

The modern lifestyle with its drastic changes in the way we eat and move puts pressure on the homoeostatic system responsible for the regulation of body weight, which has led to an increase in overweight and obesity. The power of food cues targeting susceptible emotions and cognitive brain functions, particularly of children and adolescents, is increasingly exploited by modern neuromarketing tools. Increased intake of energy-dense foods high in fat and sugar is not only adding more energy, but may also corrupt neural functions of brain systems involved in nutrient sensing as well as in hedonic, motivational and cognitive processing.

And a nice one from the conclusions:
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New Review Paper by Yours Truly: High-Fat Dairy, Obesity, Metabolic Health and Cardiovascular Disease

My colleagues Drs. Mario Kratz, Ton Baars, and I just published a paper in the European Journal of Nutrition titled "The Relationship Between High-Fat Dairy Consumption and Obesity, Cardiovascular, and Metabolic Disease".  Mario is a nutrition researcher at the Fred Hutchinson Cancer Research Center here in Seattle, and friend of mine.  He's doing some very interesting research on nutrition and health (with an interest in ancestral diets), and I'm confident that we'll be getting some major insights from his research group in the near future.  Mario specializes in tightly controlled human feeding trials.  Ton is an agricultural scientist at the University of Kassel in Germany, who specializes in the effect of animal husbandry practices (e.g., grass vs. grain feeding) on the nutritional composition of dairy.  None of us have any connection to the dairy industry or any other conflicts of interest.

The paper is organized into three sections:

1. A comprehensive review of the observational studies that have examined the relationship between high-fat dairy and/or dairy fat consumption and obesity, metabolic health, diabetes, and cardiovascular disease.
2. A discussion of the possible mechanisms that could underlie the observational findings.
3. Differences between pasture-fed and conventional dairy, and the potential health implications of these differences.

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What Causes Type 2 Diabetes, and How Can it be Prevented?

In the comments of the last post, we've been discussing the relationship between body fatness and diabetes risk.  I think this is really worth understanding, because type 2 diabetes is one of the few lifestyle disorders where 1) the basic causes are fairly well understood, and 2) we have effective diet/lifestyle prevention strategies that have been clearly supported by multiple controlled trials.

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Interview with Aitor Calero of Directo al Paladar

Aitor Calero writes for the popular Spanish cooking and nutrition blog, Directo al Paladar ("straight to the palate").  We did a written interview a while back, and he agreed to let me post the English version on my blog.  The Spanish version is here and here.

Without further ado, here it is:

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Why Did Energy Expenditure Differ Between Diets in the Recent Study by Dr. Ludwig's Group?

As discussed in the previous post, a recent study by Dr. David Ludwig's group suggested that during weight maintenance following fat loss, eating a very low carbohydrate (VLC) diet led to a higher metabolic rate (energy expenditure) than eating a low-fat (LF) diet, with a low glycemic index (LGI) diet falling in between the two (1).  The VLC diet was 30 percent protein, while the other two were 20 percent.  It's important to note that these were three dietary patterns that differed in many ways, and contrary to claims that are being made in the popular media, the study was not designed to isolate the specific influence of protein, carbohydrate or fat on energy expenditure in this context. 

Not only did the VLC diet lead to a higher total energy expenditure than the LF and LGI diets, the most remarkable finding is that it led to a higher resting energy expenditure.  Basically, people on the VLC diet woke up in the morning burning more energy than people on the LGI diet, and people on the LGI diet woke up burning more than people on the LF diet.  The VLC dieters burned 326 more calories than the LF dieters, and 200 more than the LGI dieters.

It's always tempting to view each new study in isolation, without considering the numerous studies that came before it, but in this case it's essential to see this study through a skeptical lens that places it into the proper scientific context.  Previous studies have suggested that:

1. The carbohydrate:fat ratio of the diet has little or no detectable impact on energy expenditure in people who are not trying to lose weight (2, 3).
2. The carbohydrate:fat ratio of the diet has little or no detectable impact on energy expenditure in people who are being experimentally overfed, and if anything carbohydrate increases energy expenditure more than fat (4, 5).
3. The carbohydrate:fat ratio of the diet has little or no detectable impact on energy expenditure during weight loss (6, 7, 8), and does not influence the rate of fat loss when calories are precisely controlled. 

This new study does not erase or invalidate any of these previous findings.  It fills a knowledge gap about the effect of diet composition on energy expenditure specifically in people who have lost weight and are trying to maintain the reduced weight.

With that, let's see what could have accounted for the differences observed in Dr. Ludwig's study.
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New Study: Is a Calorie a Calorie?

A new study in JAMA led by Dr. Cara B. Ebbeling and colleagues purports to challenge the idea that all calories are equally fattening (1).  Let's have a look.  When thinking about the role of calorie intake in body fatness, there are basically three camps:

1.    Calories don’t matter at all, only diet composition matters.
2.    Calories are the only thing that matters, and diet composition is irrelevant.
3.    Calories matter, but diet composition may also play a role.

The first one is an odd position that is not very well populated.  The second one has a lot of adherents in the research world, and there’s enough evidence to make a good case for it.  It’s represented by the phrase ‘a calorie is a calorie’, i.e. all calories are equally fattening.  #1 and #2 are both extreme positions, and as such they get a lot of attention.  But the third group, although less vocal, may be closest to the truth. 
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What Puts Fat Into Fat Cells, and What Takes it Out?

Body fatness at its most basic level is determined by the rate of fat going into vs. out of fat cells. This in/out cycle occurs regardless of conditions outside the cell, but the balance between in and out is influenced by a variety of external factors.  One of the arguments that has been made in the popular media about obesity goes something like this:  


A number of factors can promote the release of fat from fat cells, including:

Epinephrine, norepinephrine, adrenocorticotropic hormone (ACTH), glucagon, thyroid-stimulating hormone, melanocyte-stimulating hormone, vasopressin, and growth hormone

 But only two promote fat storage:

Insulin, and acylation-stimulating protein (ASP)*

Therefore if we want to understand body fat accumulation, we should focus on the latter category, because that's what puts fat inside fat cells.  Simple, right?

Can you spot the logical error in this argument?

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New Study Demonstrates that Sugar has to be Palatable to be Fattening in Mice

Dr. Anthony Sclafani's research group just published a study definitively demonstrating that high palatability, or pleasantness of taste, is required for sugar to be fattening in mice (1).  Dr. John Glendinning was lead author. Dr. Sclafani's group has done a lot of excellent research over the years.  Among other things, he's the person who invented the most fattening rodent diet in the world-- the 'cafeteria diet'-- composed of human junk food. 

Mice and rats love sweet food and drinks, just like humans.  If you give them a choice between plain water and sugar water, they'll overconsume the sugar water and become obese.  I have argued, based on a large body of evidence, that the reward value and palatability* of these solutions are important to this process (2, 3, 4).  This is really just common sense honestly, because by definition if the solution weren't rewarding the mice wouldn't go out of their way to drink it instead of water, the same way people wouldn't go out of their way to get soda if it weren't rewarding.  But it's always best to confirm common sense with research.
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Sugar Intake and Body Fatness in Non-industrial Cultures

Around the world, non-industrial cultures following an ancestral diet and lifestyle tend to be lean. When they transition a modern diet and lifestyle, they typically put on body fat and develop the classic "diseases of civilization" such as diabetes and cardiovascular disease.  If we can understand the reasons why this health transition occurs, we will understand why these problems afflict us today.  Research has already identified a number of important factors, but today I'm going to discuss one in particular that has received a lot of attention lately: sugar.

There's an idea currently circulating that sugar is the main reason why healthy traditional cultures end up obese and sick.  It’s easy to find non-industrial cultures that are lean and don’t eat much sugar, and it’s easy to find industrial cultures that are obese and eat a lot of it.  But many factors are changing simultaneously there.  We could use the same examples to demonstrate that blue jeans and hair gel cause obesity.  If sugar is truly the important factor, then cultures with a high sugar intake, but an otherwise ancestral diet and lifestyle, should also be overweight and sick.  Let’s see if that's true. 

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Calories Still Matter

The Centers for Disease Control's NHANES surveys documented a massive increase in obesity in the United States between the 1960-62 and 2007-2008 survey periods (1).  In 1960, 13 percent of US adults were obese, while in 2008 that number had risen to 34 percent.  The prevalence of extreme obesity increased from 0.9 to 6.0 percent over the same time period!

Something has changed, but what?  Well, the most parsimonious explanation is that we're simply eating more.  Here is a graph I created of our calorie intake (green) overlaid on a graph of obesity prevalence (blue) between 1970 and 2008:

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How Bad is Fructose? David Despain Interviews Dr. John Sievenpiper

In my article "Is Sugar Fattening?", I discussed a recent review paper on fructose, by Dr. John Sievenpiper and colleagues (1).  It was the most recent of several review papers to conclude that fructose is probably not inherently fattening in humans, but that it can be fattening if it's consumed to excess, due to the added calories.  Dr. Sievenpiper and colleagues have also written other papers addressing the metabolic effects of fructose, which appear to be fairly minor unless it's consumed to excess (2, 3, 4, 5).  The senior author on these studies is Dr. David Jenkins at McMaster University.  David Despain, a science and health writer who publishes a nice blog called Evolving Health, recently interviewed Dr. Sievenpiper about his work.

It's an interesting interview and very timely, due to the recent attention paid to fructose in the popular media. This has mostly been driven by a couple of high-profile individuals-- an issue they discuss in the interview.  The interview, recent papers, and sessions at scientific conferences are part of an effort by researchers to push back against some of the less well founded claims that have received widespread attention lately.

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