The Best Diet to Keep Weight Off

You’ve lost weight, but will you keep it off? A low-glycemic-index diet may work better than others at burning calories and helping people ward off those pesky Lbs, reports a new study in the Journal of the American Medical Association.

In the study, researchers had 21 people who’d lost 10 to 15 percent of their body weight try three different diets, each for 4 weeks. The diets consisted of a low-fat, a low-carbohydrate, and a low-glycemic-index—which endorses carbohydrates that keep blood sugar levels low—eating program.

The result: Even though the participants ate the same amount of calories on each of the plans, they burned an average of 300 fewer calories per day on the low-fat diet compared to the low-carb option.

But the low-carb diet wasn’t a win-win alternative, either. Although it was better at encouraging calorie burn, it also caused the greatest increases in cortisol and C-reactive protein levels—both of which may elevate heart disease risk—among the study participants.

The low-glycemic-index diet, however, seemed to strike the right balance in terms of heart health and resting metabolism, says study authoer Cara Ebbeling, Ph.D., associate director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital. And any help you can get torching extra calories is beneficial after a big weight loss. That's because the more weight you lose, the more your metabolism slows, making it increasingly difficult to burn calories, explains Ebbeling. (Here's the truth behind the glycemic index, a notion many experts disagree with entirely.)

So is a low-glycemic-index diet the savior for people who want to keep the excess baggage from creeping back? The problem of “weight maintenance” may not be so easily solved, warns Alan Aragon, M.S., and a Men’s Health nutrition expert. “You can’t tell a whole lot after 4 weeks,” he says. “And looking at the nutritional makeup of the diets used in the study, you’re really comparing two extremes in the low-carb and low-fat diets to a more moderate diet, which will almost always be best in the long run.”

Avoid diets that condemn whole nutrient categories, he suggests. Instead, eat proven weight-managers—whole foods like fruits, vegetables, whole grains, and nuts, as well as proteins like fish and meat. “Your body requires about ten times more energy to process a gram of protein than a gram of fat. So you’ll burn more calories just by eating more protein-packed foods,” Aragon explains. Follow our 6 Grilling Recipes for Weight Loss to cook up some of the leanest, healthiest, and tastiest dishes of the summer—and effortlessly drop pounds while you're doing it.

Exercise will also play a big role in whether you’re able to fend off the old weight, Aragon says. Running or other aerobic exercise is good, but you should mix in weight training at least half of the time. “Resistance exercise boosts lean body mass and metabolism, both of which help your body burn calories even when you’re not working out,” he says. Shoot for a minimum of three 30-to-60-minute workout sessions a week, he advises. Try the 18 cutting-edge workouts found in the Speed Shred program. They're fast-paced and designed to blast fat and light your muscles on fire.

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