My TEDx Talk, "The American Diet: a Historical Perspective"

On October 21st, I spoke at the Harvard Food Law Society's TEDx conference, Forum on Food Policy.  The conference kicked off with three talks on nutrition, by Drs. Walter Willett, David Ludwig and myself.  My talk is only 17 minutes long as per TED format, but it's packed with research on both quantitative and qualitative changes in the US diet over the last two centuries.  It contains surprises for almost anyone, and I can guarantee you've never learned this much about the history of the US diet in 17 minutes.  The talk was titled "The American Diet: a Historical Perspective"; you can access it by following that link.

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What Causes Insulin Resistance? Part V

Previously in this series, we've discussed the role of cellular energy excess, inflammation, brain insulin resistance, and micronutrient status in insulin resistance.  In this post, I'll explore the role of macronutrients and sugar in insulin sensitivity.

Carbohydrate and Fat

There are a number of studies on the effect of carbohydrate:fat ratios on insulin sensitivity, but many of them are confounded by fat loss (e.g., low-carbohydrate and low-fat weight loss studies), which almost invariably improves insulin sensitivity.  What interests me the most is to understand what effect different carbohydrate:fat ratios have on insulin sensitivity in healthy, weight stable people.  This will get at what causes insulin resistance in someone who does not already have it.

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High-Fat Diets, Obesity and Brain Damage

Many of you have probably heard the news this week:

High-fat diet may damage the brain
Eating a high-fat diet may rapidly injure brain cells
High fat diet injures the brain
Brain injury from high-fat foods

Your brain cells are exploding with every bite of butter!  Just kidding.  The study in question is titled "Obesity is Associated with Hypothalamic Injury in Rodents and Humans", by Dr. Josh Thaler and colleagues, with my mentor Dr. Mike Schwartz as senior author (1).  We collaborated with the labs of Drs. Tamas Horvath and Matthias Tschop.  I'm fourth author on the paper, so let me explain what we found and why it's important.  

The Questions

Among the many questions that interest obesity researchers, two stand out:

1. What causes obesity?
2. Once obesity is established, why is it so difficult to treat?

Our study expands on the efforts of many other labs to answer the first question, and takes a stab at the second one as well.  Dr. Licio Velloso and collaborators were the first to show in 2005 that inflammation in a part of the brain called the hypothalamus contributes to the development of obesity in rodents (2), and this has been independently confirmed several times since then.  The hypothalamus is an important brain region for the regulation of body fatness, and inflammation keeps it from doing its job correctly.

The Findings

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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.

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Food Reward: a Dominant Factor in Obesity, Part III

Low-Fat Diets

In 2000, the International Journal of Obesity published a nice review article of low-fat diet trials.  It included data from 16 controlled trials lasting from 2-12 months and enrolling 1,910 participants (1).  What sets this review apart is it only covered studies that did not include instructions to restrict calorie intake (ad libitum diets).  On average, low-fat dieters reduced their fat intake from 37.7 to 27.5 percent of calories.  Here's what they found:
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Clarifications About Carbohydrate and Insulin

My statements about carbohydrate and insulin in the previous post seem to have kicked up some dust!  Some people are even suggesting I've gone low-fat!  I'm going to take this opportunity to be more specific about my positions.

I do not think that post-meal insulin spikes contribute to obesity, and they may even oppose it. Elevated fasting insulin is a separate issue-- that's a marker of insulin resistance.  It's important not to confuse the two.  Does insulin resistance contribute to obesity?  I don't know, but it's hypothetically possible since insulin acts like leptin's kid brother in some ways.  As far as I can tell, starch per se and post-meal insulin spikes do not lead to insulin resistance.
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