Can a DNA Test Help You Find the Right Diet?

Most diet programs take a one-size-fits-all approach. Considering that nearly 70 percent of Americans are overweight or obese, that size is often extra-large.MORE: 10 Ways to Lose WeightSo we wondered if taking a more personalized approach to weight loss by trying Inherent Health’s new Weight Management Genetic Test might be the ticket.The test involves swabbing the inside of your cheek in exactly the same way you’ve seen it done hundreds of times to suspects on Law & Order and CSI. Only instead of shipping your saliva-coated Q-tip off to a police lab, you send it to the Interleukin Genetics, Inc. lab, Inherent Health’s parent company, in Waltham, Mass., where an analysis of your genetic code places you in one of six possible weight loss categories: low carb-moderate exercise; low carb-high exercise; low fat-high exercise; low fat-moderate exercise; even balance of carb/fat-moderate exercise; or even balance of carb/fat-high exercise.From there, a detailed report explains the right diet and exercise regimen for your particular genetic profile. For example, my report informs me that my diet identity is “Fat Trimmer” and my exercise identity is “High MET.” This means I’m likely to shed the most pounds by limiting fat intake and engaging in high-intensity workouts.As Interleukin’s president and chief scientific officer Ken Kornman, Ph.D., explains it, I still need to cut back on overall calories and watch out for the so-called ‘bad carbs,’ including sugar and white flour. “Within that construct, following the specific recommendations for your weight loss type significantly increases your chances of successfully losing weight,” he says.But can a simple cheek swab really guarantee all that?What Your Genes Say About Your HealthGene testing can reveal a lot about a person’s health. Scientists are able to decode genes associated with the risk of everything from cancer to stuttering. So why shouldn’t they be able to decipher how our bodies respond to different combinations of food and exercise?MORE: Are Some People Born to be Thin?And certainly there’s no denying that genetics plays a considerable role in each individual’s battle of the bulge. Although estimates vary, most experts agree that at least 40 to 60 percent of the variation in what a person weighs can be chalked up to differences in DNA. This variation explains why two people who go on the same diet and exercise plan can have vastly different results.The Inherent Health team decided to hunt down the genes with the strongest evidence for their effect upon body weight and metabolism. They started by examining hundreds of gene variations that have published data associating them with weight and metabolism. Then, using a strict set of criteria, they whittled down the list of possible suspects to just three genes related to diet and two related to physical activity.“These are the genes included in our test because they’re the only ones where the evidence was strong enough to support their influence on body weight,” explains Kornman.Kornman concedes there isn’t a way to prove the validity of the physical activity genes they selected, but to further validate their choice of dietary-influencing genes the company sponsored a series of clinical trials. One trial performed at Stanford University looked at 141 women on four different diets: Atkins (ultra-low-carb), the Zone (low-carb), Ornish (very low-fat) and a low-fat diet following the federal Food Pyramid. The women gave DNA samples as well.After a year, the women whose diets matched their genetic makeup lost 2.5 times more weight than the women whose diets didn’t match—13.2 pounds versus 4.5 pounds, respectively.Is It a Big Stretch?This preliminary evidence hasn’t convinced some experts. Trials have been relatively small and not diverse enough to account for possible genetic disparities between the sexes or ethnic groups. Plus, even if a sort of “biological determinism” has a strong influence over how many pounds are gained and lost, Ruth Loos, Ph.D., a genetic epidemiologist who is the director of the genetics of obesity and related traits program for Mt. Sinai Hospital in New York City, thinks it’s still a big leap to claim this information can be used to create individualized weight loss plans.MORE: Six Apps That Help You Lose Weight“We don’t yet have sufficient genetic information to personalize diet based on individual genes,” Loos states. “Certain genes are validated for their association with weight loss and certain diets, but we know from the scientific literature that this doesn’t mean that there’s enough data to help predict what diet is best for you.”FABP2, one of the dietary genes included in the Inherent Health test, is a good illustration of how basing a diet on DNA can be misleading.My report revealed that I have the “A,G” variant of this gene, which is generally associated with people who have a higher than average body mass index and who tend to hold onto the calories in dietary fat more stubbornly than those who possess other variants of FABP2. However, I’m not overweight. I never have been despite the fact I’m a lifelong fatty-food addict.“We can’t simply take general observations and translate them to one particular person,” Loos points out. ”Just because one gene had a significant association with a weight loss response in a population doesn’t tell you much about how the gene will express, how it will interact with other genes or whether that gene will have a strong impact on your response to a diet as an individual.”Biology Versus BehaviorOf course, there is also the question of behavior. Is biology destiny or can you change the fate of your dress size by the choices you make? On this point, there seems to be total agreement: No test is a free pass from the hard work that goes into losing weight and keeping it off.MORE: How Much Exercise Do You Really Need?Even Kornman stresses the importance of good lifestyle habits and cautions that the test only provides a blueprint—one that is far from perfect but one that Inherent Health hopes to improve over time by adding more information about additional genes. “Knowing more about your weight loss type can help clear up a lot of the mixed messages that confuse dieters and steer them toward dead end solutions,” he says. “It can give you an edge but you still have to commit to making lifelong changes.”The Bottom LineI might consider making a few tweaks to my health regimen based on my report, but at the moment I’m not sure I have the motivation to give up peanut butter and pizza. Besides, I think many dieters may find the test almost incidental. What they may appreciate more is having an explicit, step-by-step plan to follow, plus the excellent coaching tools Inherent Health provides, including a consultation with a weight loss counselor and helpful calculators, charts and graphs to help track calories consumed and burned.Numerous studies show that this type of support can help you lose more weight than you would on your own and can substantially increase your chances of keeping it off.  At $169, it’s also less pricey than many other weight loss methods that have a lot less science behind their recommendations.And surprisingly, even though Loos doesn’t feel such tests provide meaningful information for choosing a weight loss plan, she isn’t necessarily against them. “While I don’t believe we can currently make accurate predictions using genotype data in the context of diet, exercise and lifestyle,” she says, “if people adopt a better, healthier lifestyle than they did before the test, then I think it has achieved something we should applaud.”