Your Health

Genetically Determined Dieting? Maybe Not Yet

Hand grabbing a big burger i i

At least low-carb and low-fat diet fans both agree that you should stay away from this. (iStockphoto.com) hide caption

itoggle caption (iStockphoto.com)
Hand grabbing a big burger

At least low-carb and low-fat diet fans both agree that you should stay away from this.

(iStockphoto.com)

They may not be the Montagues and Capulets, but fans of low-fat and low-carb diets have been locking horns for quite a while. But now, researchers at Stanford University claim they've found a way to resolve this bitter rivalry: look at your genes.

They say that a simple genetic test may predict which diet works best on a case-by-case basis.

"It's a step closer to realizing personalized nutrition for weight loss," Christopher Gardner, associate professor of medicine at Stanford, told Shots.

Results from the study he helped conduct were presented at an American Heart Association conference last week. The work, which got a lot of attention in the popular press, hasn't been published in a peer-reviewed journal yet.

But we wanted a second opinion, and turned to Nanette Steinle, an endocrinologist at the University of Maryland med school. She agrees that the test shows promise, but says it's far too early to start offering it to the public.

"I think it's hopeful that we've uncovered additional understanding of why some people respond to a particular diet better than others, but we're not at a point today to start implementing this in practice," Steinle said.

One of the reasons Steinle says she's just not ready to recommend testing is the small sample size of women tested in the Stanford study — 138, to be precise.

Still, if you've got the money and the curiosity, nobody can stop you from trying it. The test, developed by Interleukin Genetics, requires a swab of the cheek and $149. Interleukin, for what it's worth, also sponsored the study, but you probably guessed that already.

Oh, there's one other thing. This new study isn't completely new. "It's retrospective," Gardner said. Back in 2007, Gardner published a study in the Journal of the American Medical Association on the long-term results of low-carb, high-protein, high-fat diets. At the time NPR's Patti Neighmond took a close look.

According to Neighmond, in that study, 311 women who were 15 to 100 pounds overweight were randomly assigned to one of the diets. After a year, Gardner assessed the women's health and weight.

While the study gave a slight edge to the low-carb diet, Gardner says that weight-loss varied more within each diet than it did between the different approaches. "Within each diet group in our study the range of success was 40 pounds. Some women lost a bunch of weight, some women even gained some," he said.

But last year, Interleukin execs called Gardner up and told him about their new test. The company claimed that it had come up with a classification system for weight-loss genes. They put dieters in three genetic baskets, according to which approach might work best: low-carb, low-fat and balanced. Interleukin wanted to reevaluate the people in Gardner's study based on their criteria.

So Gardner's group contacted them; 141 of those initial 311 women said OK. They swabbed the inside of their cheeks to get DNA samples and sent them in. Turns out that three did it wrong, so the final number of samples was 138.

Gardner agreed that a lot more research needs to go into getting this sort of testing ready for prime time. In fact, he's already planning a larger study.

But, he said it was encouraging that of the women tested in this preliminary study, only five fell in the "balanced" group and the rest were divided 60-40 into the low-carb and low-fat genotypes respectively. "And that actually enriched the story tremendously," Gardner said, because it means that almost half of dieters could respond badly to their diet of choice—if they happened to choose badly. That finding, he said, helped make sense of the huge variations in the study's original results, he said.

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