Are Diets Based on Your Genetics Worth It?

Elite new diet programs promise more effective weight loss with plans so personal they're based on your genetic response to food and exercise. Is this a true scientific breakthrough, or just another way to waste your precious time and money?

DNA dietsDNA dietsA friend of mine was recently railing against the epidemic of obesity in America-about one third of Americans are obese and another third overweight-and thought she'd identified the culprit: fat people. "I don't understand why they don't just exercise some self-control," she said, sliding easily between two tables and into a banquette, a margarita in hand. This friend is blond, smooth-skinned, always immaculately dressed, and, of course, model-thin-"your basic nightmare," as Nora Ephron put it.

"I don't think people have that much control over their weight," I said. Nearly 20 percent of American children are obese-hardly their fault-and obese children are at a much higher risk of becoming obese adults. I told her that I once profiled a woman who got bariatric surgery and would never forget her almost suicidal despair every time she regained weight she'd lost, or her obsessive regimen to maintain her post-surgery size. After knowing her, I could never look at an obese person without immense sympathy or watch The Biggest Loser without weeping buckets. "Maybe you just have great genes," I told my friend. "Look at you." Mollified by the compliment (and the cocktail, no doubt), she dropped the subject.

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Though I'm not a willowy beauty like my friend, I've always figured I have decent genes too. Outside of pregnancy, I've been the same weight since high school, give or take five pounds. So when I heard about two programs that promise to analyze your genes and then make diet and exercise recommendations, I anticipated good news-"Eat anything you want, lucky girl!"-not to mention more ammunition for my next argument with my friend. ("See? My weight isn't willpower; it's fate.")

How Genetics-Based Diet Plans Work

Interleukin Genetics, a Massachusetts-based company, sends out a do-it-yourself box for $169. You swab your cheek with a little mascara-brush-like doohickey and mail it to a lab to be analyzed for five genetic variations on four genes. Among 200-odd genes so far identified to influence weight, Interleukin chose the ones that company officials said had the steepest piles of evidence. Two of the variations relate to the body's use of fat during exercise; the others help determine predisposition for diabetes and weight gain, and how the body absorbs fatty acids from food. The results arrive in two weeks, with recommendations for diet (low-fat, low-carb, or balanced) and the exercise you need to mobilize fat stores: Are you one of those who can stay slim with moderate walking, or do you need to run your system a little hotter to burn fat?

The company bases its test on research it piggybacked on a Stanford University study that compared four diets-Atkins, Zone, Ornish, and a standard government-recommended program-in obese and overweight women and found them all about equally effective. Interleukin tested the women for the five genetic variations and turned up three patterns, with one group losing more weight on Atkins, another on Ornish, and the third on one of the more balanced diets. They then did another small study, putting about half of 34 individuals in an employee weight-loss program on a diet based on the Stanford patterns. This time, the DNA-matched dieters lost twice as much as those on a standard regimen. The company plans to publish its data within the next year.

Newtopia, a Canadian firm that recently launched in the United States, takes a slightly different approach. You get an initial workup with a participating physician that includes a psychological and behavioral survey and a genetic test (this one involves collecting about a tablespoon of spit in a vial) for $399. Your results, a diet plan, and a month's supply of vitamin supplements come a few weeks later, augmented by six online "coaching sessions."

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Which Genes Influence Weight Gain?

Newtopia chose three genes to examine, one for each prong of its program: fitness and diet, eating behavior, and food psychology. So one gene assesses obesity risk, diabetes proclivity, and fat absorption; another how quickly your stomach lets your brain know it's full; and the third dopamine activity in the brain, to gauge whether you're among the easily satisfied or inclined to addiction and compulsivity. In addition to addressing whether your diet should be low-carb, low-fat, etc., the plan suggests behavioral changes (for example, those with lazy satiety signaling should eat more slowly, while addictive types should avoid "trigger" foods).

The claims sound impressive (if impossible to verify), and these days, when it seems like every week brings news of another disease or trait directed by our genes-from cancer to conservative political leanings-why not our diet? But calls to genetics and obesity experts quickly doused my enthusiasm for DNA diet-typing, as well as my theory that body weight is predestined.

Obesity's Biggest Culprit: Genetics or Lifestyle?

Michael Dansinger, MD, assistant professor at Tufts School of Medicine and nutrition consultant for The Biggest Loser, opined that weight is 10 percent genetics and 90 percent lifestyle. While he agrees that, evolutionarily, heavier people would have had an edge over leaner folk, the difference can't be that great-otherwise, those with "skinny genes" wouldn't have survived to pass their genes on. In essence, everyone's at risk for becoming fat in modern society, just some more than others. Our understanding of the interaction between food and genetics is "in its infancy," he said, "but even as we learn more, knowing your genes is always going to remain a minor consideration."

Dansinger coauthored a well-known study in The Journal of the American Medical Association comparing the Atkins, Ornish, Weight Watchers, and Zone diets and reported, similar to Stanford, that none of them was better than any other. The only factor that mattered was whether people stuck to their diet, and Weight Watchers and the Zone, the more moderate of the bunch, had the best adherence. So, Dansinger reasons, the ideal diet isn't in your genes; it's the one that fits your food preferences and lifestyle.

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The Hunter/Farmer Diet Solution, a new book by Mark Liponis, MD, the corporate medical director of Canyon Ranch Health Resorts, is founded on the idea that body types, evolved over millennia, fall into two basic groups: the hunter (who does better with limited carbs) and the farmer (who should opt for a low-fat, grazing-style diet). Our body types are genetically determined, he says, but not just by inheritance. Everything from what happened while we were in our mother's womb to environmental and other stressors interacts with our genes and causes some biological tendencies to be expressed more than others, Liponis argues. Instead of ordering tests, he says that he prefers to look at the way a patient presents in his office and offers a simple list of questions to assess health risks and dietary obstacles: Are you apple or pear shape? Are you hungry all the time? Crave sweets? What are your blood lipid levels? How about fasting glucose? He'd need a genetic test only to determine what diet to recommend for patients so healthy and thin that they don't have any markers for disease. But then, Liponis points out, "If someone is healthy and thin, they're probably naturally doing the right things, so why put them on a diet?"

The Truth About Lasting Weight Loss

The scientists behind Interleukin and Newtopia, not surprisingly, disagree with such critiques. "We do not for a second claim that this is the end-all, be-all of genetics in body weight," says Kenneth Kornman, president and chief scientific officer of Interleukin. "But our data clearly indicate that if people have a diet that matches their pattern, the likelihood of success is significantly greater in terms of long-term weight loss than if they're just out there randomly picking diets."

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Jeff Ruby, founder and CEO of Newtopia, concurred with Dansinger that the genetic contribution to weight is much smaller than lifestyle. But, he said, every bit helps when you're trying to do something as hard as shed pounds and keep them off.

Finally my results came in. Of the five genetic variations tested by Interleukin, I carried four of the high-risk ones. Of Newtopia's three, I carried a risk variation in two. I was stunned. I checked with the companies to see if maybe these were genes that, in truth, everyone carries. But no, the incidence among Caucasians (I'm white) ranged from about 20 percent to 30 percent. I e-mailed a friend who'd also tried one of the tests and describes herself as perpetually "chubby," and yet, she wrote back, she carried only one of the danger genes.

Reading the literature on my genetic variations, I found alarming evidence of increased risk for obesity and its complications: cancer, diabetes, heart disease. Both companies recommended a low-carb diet, but I've been a vegetarian or vegan for long stretches of my adult life. Had I been doing harm to my blood glucose levels and arteries? Later in life, would my waistline bulge, my blood pressure soar?

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Nobody from either company seemed ruffled to learn I was relatively fit despite being riddled with obesity genes. Newtopia's Ruby said he had the exact same genetic profile as I did and also had never had a weight problem. "It's not that you're predetermined to gain weight, it's just that you have genetic vulnerabilities," he said. He and Kornman both said I was likely living a far healthier lifestyle than I gave myself credit for. When I thought about it that way, I stopped feeling so bad about my genes and started patting myself on the back for my healthy ways. I'm a very consistent exerciser, I thought, and my mother is a nutritionist, so I was raised in a house without Doritos or Coke, one where vegetables dominated every meal and crash dieting was forbidden-maybe the effects were more durable than I'd realized.

Are DNA Diets Worth the Money?

So was my blond friend right? Should we blame our epidemic of obesity on bad habits alone? "It's not true either way," said Wendy Chung, MD, PhD, an assistant professor of pediatrics at Columbia University and an expert on genetics and obesity. We'd spoken earlier, and now, as I breathlessly read off my results to her, she couldn't help but giggle. "I'm sorry, I'm not laughing at you. I'm just laughing at how predictable this was. I told you that you'd get back gibberish!" Since scientists have so far turned up about 200 genes involved in body weight, how could testing for eight variations be useful? "What about the other 180 or so?" Chung said. "They could say something totally different. Tell your readers not to waste their money or time. I feel bad because I know there are a lot of desperate people, but this is just a total scam."

Robert Eckel, MD, professor of cardiology at the University of Colorado School of Medicine, took more of a wait-and-see approach. When Dansinger's paper comparing popular diets came out in 2005, Eckel wrote an accompanying essay suggesting that "nutrigenomics" might be the future of weight loss but "at present, there are no data to help clinicians practicably match a diet to an individual patient's 'diet response genotype.' " Though he was aware of Interleukin's collaboration with Stanford, he said that his stance has not changed. The data the companies are relying on first must be published, then validated by other scientists. "There might be some value here, it's just not ready for prime time," he said. "When we're talking about medicine, I like to make recommendations based on evidence. But some people like to gamble, and sometimes they win the jackpot. In gambling terms, this is still a long shot."


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