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Is There a Low-Carb Diet Gene?

There have been reports in the media in the last few days about a study from Stanford University (presented at an American Hearth Association conference in San Francisco last week). Because the study has not yet been published, I do not have access to is, but here is what I can gain from other reports: 138 overweight women were assigned to one of four diet groups. The diets were modeled after three popular diets (Atkins, Zone, and Ornish) and the U.S.D.A Food Pyramid. In this way, the researchers apparently attempted to include diets which were very low carb, very low fat, moderately low carb, and "standard diet recommendations". In terms of weight loss, the results were what we usually see in diet studies - some weight loss, and no big difference between the groups. But then came the big twist. Of the hundreds of genes which have been associated with obesity, the researchers chose three which were judged to potentially have an impact on how individuals metabolize food. When these genes were analyzed in the study participants, the whole picture of weight loss shifted. As Jennifer Thomas of HealthDay reports: "Women assigned to the correct diet based on their genotype lost two to three times more weight at 12 months than those who were assigned to a diet that was inappropriate. When the researchers looked at only the most extreme diets (Atkins versus Ornish), the results were even more stark. Women assigned to their correct diet for their genotype lost five times as much weight as those on the incorrect diet, the study found." Now, before anyone gets too excited, the researchers are emphasizing that this is a very prelininary study, and lots more work needs to be done before anything conclusive is discovered. I would also point out that this is not yet a peer-reviewed study (that is, it has not been published in a scientific journal). However, it is obviously fascinating, and potentially ground-breaking, possibly changing our whole view of who should be eating what. Some of my reflections: There have already been a few studies which have looked at different diets for different groups of people - for example, a small 2005 study showed that people who were insulin resistant lost more weight on a low-carb diet, while people whow were normal in terms of insulin did better on a low-fat diet. It also makes sense that the people who are going to benefit the most from cutting carbs have underlying issues with insulin and glucose. People who don't process sugar well simply do better with less of it, and all carbs are sugar. So I would guess that some of these genes are involved with carbohydrate/sugar metabolism. Some of the genes in the study are apparently involved with fat metabolism, which also makes sense in terms of what kind of diet would be best for an individual. One of the frustrating things about large diet studies is that while we are told the differences in the outcomes between the diet groups (which is often small), we are usually not even given hints of how much difference in outcome there was between the people within each diet group. This is potentially very important. If some people did great and some did terrible, ...
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