Drawn To Sweets Or Fats? Blame Your Genes

A new study published in the American Journal of Clinical Nutrition finds certain genes may predict a person's food choices and eating habits. Two genes in particular, which are associated with obesity, were significantly associated with more snacks per day from fats and sweets — as well as more servings from dairy and meat.

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If you ever find yourself drawn to certain foods, say you crave fats or sweets, part of it might be explained by your genes. A new study published in the American Journal of Clinical Nutrition finds some evidence that genes might be influencing our eating habits. Here's NPR's Allison Aubrey.

ALLISON AUBREY, BYLINE: In recent years, researchers have identified a few dozen genes that are associated with the development of obesity. And in many cases it's not clear how. A team at Brown University decided to try and find out how many might be playing a role in what we choose to eat.

In order to investigate this, they took blood samples from some 2,000 overweight volunteers and performed genetic testing. Researcher Jeanne McCaffery says what they found was intriguing. Certain versions of two genes, one called BDNF and another known as FTO, stood out.

JEANNE MCCAFFREY: So the FTO gene is probably the most prominent obesity gene that's been identified. And in our study we showed that individuals who had these high-risk genetic variants ate a greater number of meals and snack throughout the day. They also had higher caloric intake, and they had a greater percentage of calories from fat in their diet.

AUBREY: Particularly sweet, buttery foods. McCaffery explains that all the participants completed a questionnaire detailing how much and how often they ate different kinds of foods. Now, before you jump to the conclusion that one or two risky genes can completely explain our appetites and eating habits, McCaffery points out that the size of the effect here is small. We're not talking thousands of calories. Compared to people who didn't have the risky variants of the genes, the people who did....

MCCAFFREY: Consumed approximately 100 more calories per day than those who had lower risk markers.

AUBREY: So is 100 calories really significant? Is that going to spell the difference between someone who maintains a normal weight and someone who goes on to become obese?

MCCAFFREY: Well, it clearly depends on all the other factors in the equation, but one would anticipate that, you know, if everything else is equal and you're eating 100 more calories per day, certainly that would contribute to weight gain over time.

AUBREY: Clearly, there's a lot to be learned here. And I asked Matthew Gillman, who runs an obesity prevention program at Harvard Medical School, to weigh in on the significance of studies like this one.

MATTHEW GILLMAN: Well, this is a very well done study.

AUBREY: And Gillman says he'd like to see if the results hold up in other groups of people. But he says, just because a gene is associated with a certain behavior or liking, it does not mean it's the direct cause. Think about families. Yes, they share genes, but they also share eating habits.

GILLMAN: So if you grow up in a family where your parents or your siblings are eating a certain way, then you wind up eating that way too. And the genes are just along for the ride.

AUBREY: Gillman says an important message for anyone who diets or works hard to manage their weight is that even if some genes are playing a direct role, perhaps by influencing appetite, they are certainly not destiny.

GILLMAN: If you add up all the genes that people have related to obesity it doesn't predict a lot of the development of obesity in an individual. I think people were hoping that we could use genes to stratify risk - to say, well, you're at higher risk and you're at lower risk; we can't really do that so far.

AUBREY: And even if genetically some of us do face steeper challenges, there have been enough diet studies to show that for most people weight can be managed.

Allison Aubrey, NPR News.

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