NIH Study: Calories, Not Content, Determine Weight Loss

You aren't what you eat. You're how much.

That's the message from a two-year National Institutes of Health-funded study that assigned 811 overweight people to one of four reduced-calorie diets and found that all trimmed pounds just the same. It didn't matter what foods participants ate, but rather how many calories they consumed.

An intense debate has long raged over which dieting regimen is best. Low carb? High protein? Low fat? But the federal study, one of the longest of its kind, "really goes against the idea that certain foods are the key to weight loss," says Frank Sacks, principal investigator and a professor of cardiovascular-disease prevention at Harvard School of Public Health. "This is a pretty positive message. It gives people a lot of choices to find a diet they can stick with."

The study, published Thursday in the New England Journal of Medicine, put participants on one of four diets: Two were low fat and two were high fat, and each of these included either a high-protein or an average-protein component. Carbohydrate intake ranged from 35% to 65%. All the diets were low in calories and saturated fat, and high in fiber, and participants were asked to exercise a fixed 90 minutes a week.

Patients, who attended counseling sessions, lost an average of 13 pounds after six months. After two years, they had lost nine pounds on average and trimmed two inches off their waists regardless of which diet they followed. The study, which ended December 2007, was conducted in Boston at Brigham and Women's Hospital, and in Baton Rouge, La., at Pennington Biomedical Research Center.

In the study, doctors calculated each participant's energy needs, and structured a diet that had 750 fewer calories than would be necessary to fuel his or her activity. Typical diets in the study had between 1,400 and 2,000 calories a day.

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