The promise of mining our genetic code to prevent disease (see: the Human Genome Project) is taking a back seat to the breakthrough the fitness-obsessed have been waiting for: using our genes to fight fat. Although science has demonstrated that low-carb diets (Dr. Atkins is the forefather) and low-fat diets (pushed hardest by Dr. Dean Ornish) can be effective, research also shows they don't work equally well for everybody. A Stanford study suggests that DNA may be a big piece of the one-size-doesn't-fit-all puzzle: Subjects who ate a diet tailored to their genetic type lost twice as much weight as those whose diets and genes were not in sync. If having your genes analyzed to slim down sounds like science fiction to you, consider these three accessible and increasingly popular new ways to get diet and fitness advice based on your DNA.


At the doctor's office

The Concept
The San Diego-based lab Pathway Genomics has crunched the academic-research literature and come up with a procedure that looks at 80 genetic markers that affect the way the body processes carbs, fats, and protein and how it will likely respond to exercise. You hand your trainer a test tube of saliva and $400 and complete a lifestyle-and-health questionnaire, then Pathway sends the customized diet-and-exercise report to your doctor. The company recommends one of four diets: low-fat, low-carb, Mediterranean (heavy on the "good" fats found in fish and olive oil), and balanced (a generic healthy diet). You (or your doctor) can discuss the results with a Pathway genetic counselor or nutritionist, for no extra charge.

The Plan
About 30 percent of Pathway's clients are prescribed a low-fat regimen: Because their bodies don't do a good job of breaking down and processing fats, they're put on a diet that skimps on animal fats, dairy, and fried foods, which should decrease the amount of LDL, a.k.a. bad cholesterol. They pick up the caloric slack with fruits, vegetables, and whole grains. Low-carb candidates (another 30 percent of Pathway clients) don't efficiently chop up complex carbohydrates to burn as energy, which means some of the carbs are converted into fat. This group is advised to steer clear of breads, cereals, and grains and close the caloric gap with lean, clean protein (fish, poultry), fruits, and non-starchy veggies. The Mediterranean diet is tailored to the 20 percent of clients whose genes don't point them toward low-fat or low-carb diets but predispose them to receive a greater-than-average health boost from good-for-you fats, which raise their HDL levels—hence the plan's emphasis on fish, nuts, and olive oil. The remaining 20 percent of people are put on Pathway's balanced diet, because their genes have no telling variations. This all-purpose, textbook healthy plan loads up on brightly colored produce (carrots to cantaloupe, blueberries to broccoli), whole grains like quinoa and brown rice, fish, beans, and lean poultry.


At the gym

The Concept
At Equinox health clubs in Los Angeles' Century City and Greenwich, Connecticut (and coming eventually to most of the chain's gyms across the country), you produce $300 and a test tube of saliva. Your sample is sent to the L.A.-based preventive-medicine company Existence Genetics, which looks for variations in your genes that indicate everything from your chances of developing arthritis to your risk of toppling over from a heart attack on the treadmill. The results help you choose the right diet-and-workout regimen.

The Plan
The gym will recommend a customized training-diet program. Surprisingly, it's Equinox's younger, seemingly in-the-know clientele who are the most in the dark. "We find that our younger males are the ones with the least sophisticated knowledge relative to nutrition," says Matt Berenc, fitness manager at the Century City club. "So we spend a lot of time working with this assessment to show them how to eat right, be it low-carb or low-fat," Berenc says. "People will join a gym, will have goals—whether it's to lose weight or get healthy. This gives them a little more kick in the butt."


At home

The Concept
In his new book, The Hunter/Farmer Diet Solution, Dr. Mark Liponis, medical director for the Canyon Ranch spas, has outlined a low-tech way to make the low-carb/low-fat call. He discerns your genetic type with routine annual lab tests and by eyeballing body shape, which he believes can reveal your evolutionary history. If you're a "hunter," you carry your weight in your belly, mostly because you process sugar slowly, which allowed your ancestors to retain their blood-sugar levels, and thus their energy, between kills. The results of your annual physical will probably include higher-than-average triglycerides. But if you have more "farmer" genes, you tend to pack pounds on your thighs and buttocks, even though you're a doctor's-office high performer (healthy cholesterol, triglyceride, and blood-sugar readings). Your ancestors' bodies adapted over millennia to handle grains and cereals in a way that quickly converts carbs into energy.

The Plan
To lose weight, hunters need to cut back on refined carbs, which keep blood-sugar and insulin levels too high and send you down the pre-diabetic path. "If your ancestors couldn't hunt it or forage it, don't eat it," Liponis says. Stay on the hunter schedule—eating fewer and bigger meals (read: when you get a kill). Farmer types, on the other hand, need to avoid overdoing high- calorie, artery-clogging animal fats, eating baked potatoes instead of fries, broiled chicken and fish instead of fried. They can graze as often as they like (granolas, berries, and nonfat yogurt are perfect) to boost energy levels.


The Controversy: Does It Work?

YES: "A lot of the data is not ready for prime time, but there probably is value added," says Dave Kaufman, of Johns Hopkins' Genetics & Public Policy Center. Cardiologist Samir Damani, who offers Pathway testing at his San Diego practice, says genetic data adds "granularity and accuracy" to his diet and exercise advice. "It's a hell of a lot better than a doctor recommending whatever fad diet is going around," he says.

NO: "I'd still call it recreational genetics," says Dr. Joann Bodurtha, a visiting professor in the McKusick-Nathans Institute of Genetic Medicine at Johns Hopkins University. "The science has gotten better, but what bothers me is the potential overpromising. I don't see any data to suggest that you wouldn't do better spending your money on a nutritionist."

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