Tuesday, September 15, 2015

Out for Two Weeks

I'll be out of town with limited internet until September 27th.  Feel free to leave comments, but I won't be able to moderate them until I return.  Sorry for the inconvenience!

Wednesday, August 26, 2015

How Much Does Sugar Contribute to Obesity?

Last week, the British Medical Journal published a review article titled "Dietary Sugars and Body Weight", concluding that "free sugars" and sugar-sweetened beverages contribute to weight gain.  But what are "free sugars", and why does the scientific literature suggest that the relationship between sugar intake and body weight isn't as straightforward as it may initially appear?

Tuesday, August 18, 2015

More Thoughts on the Recent Low-fat vs. Low-carb Metabolic Ward Study

The recent low-carb vs. low-fat study has provoked criticism from parts of the diet-health community.  Let's examine these objections and see how they hold up to scientific scrutiny.

Thursday, August 13, 2015

A New Human Trial Undermines the Carbohydrate-insulin Hypothesis of Obesity, Again

The carbohydrate-insulin hypothesis of obesity states that carbohydrates (particularly refined carbohydrates and sugar) are the primary cause of obesity due to their ability to increase circulating insulin, and that the solution to obesity is to restrict carbohydrate intake.  Numerous studies have tested this hypothesis, more or less directly, in animals and humans.  Despite the fact that many of these studies undermine the hypothesis, it remains extremely popular, both in the popular media and to a lesser extent among researchers.  A new human trial by Kevin Hall's research team at the US National Institutes of Health offers very strong evidence that the carbohydrate-insulin hypothesis of obesity is incorrect.  At the same time, it offers surprising and provocative results that challenge prevailing ideas about diet and weight loss.

Saturday, July 25, 2015

Refined Sugar Worsens Blood Lipid Markers of Cardiovascular Disease

Blood lipids such as LDL and HDL cholesterol are markers of the biological processes that impact cardiovascular disease, and they are commonly measured to assess cardiovascular risk.  When we think about the impact of food on blood lipids, dietary fat typically comes to mind.  Yet a new study shows that dietary carbohydrate, specifically high-fructose corn syrup, can have a large impact on blood lipid markers of cardiovascular disease risk.


Dietary fats have well-established impacts on blood lipids.  For example, in short-term feeding trials, saturated fat tends to increase total cholesterol, increase LDL ("bad") cholesterol, and increase HDL ("good") cholesterol, while the omega-6 polyunsaturated fat linoleic acid decreases total cholesterol and decreases LDL cholesterol.  For this reason, dietary advice to reduce cardiovascular risk tends to focus on dietary fat.

The hypothesis that refined dietary sugar is harmful to the cardiovascular system isn't new.  In 1972, British physiologist and nutrition researcher John Yudkin published a classic book called Pure, White, and Deadly, which argued, among other things, that refined sugar is harmful to the cardiovascular system.  Yet at the time, the supporting data were weak, and the hypothesis was never taken very seriously by the scientific community.

Peter Havel and his group at UC Davis have begun to breathe new life into this hypothesis with their rigorous work on the cardiovascular effects of dietary sugars.

Tuesday, July 7, 2015

What Properties Make a Food "Addictive"?

Although the concept of food addiction remains controversial, there's no doubt that specific foods can provoke addiction-like behaviors in susceptible people.  Yet not all foods have this effect, suggesting that it's related to specific food properties.  A new study aims to identify the properties that make a food "addictive".