Which Diet Works Best?

Some beat others at keeping off the weight

Jennifer Anderson

AARP Bulletin

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En español

Published July 19, 2012

Health Discovery: Low-Glycemic Diet May Be Best

A low-glycemic diet may be the best option to help keep the pounds off.

Photo by David Prince/Getty Images

The hardest part of dieting — keeping off the weight — may be easier if you follow a diet that actually helps you burn more calories, a new study suggests.
The study by Boston Children's Hospital researchers published last month in the Journal of the American Medical Association looked at three types of popular diets — low-fat, very-low-carb and low-glycemic — to see which ones boosted people's metabolism to help keep off the pounds.

The result was sort of a Goldilocks-and-the-three-diets tale, with the low-glycemic diet deemed "just right."

Senior researcher David Ludwig, M.D., director of the hospital's New Balance Foundation Obesity Prevention Center, explains that your metabolism — all the bodily chemical processes that maintain life and, in doing so, burn calories — tends to slow down after weight loss, which can then lead dieters to regain lost pounds. But "by eating right," Ludwig says, "you can improve your metabolism and decrease hunger, thereby making weight-loss easier."

Researchers had 21 overweight adults first lose 10 to 15 percent of their body weight. The participants then followed each of the diets for a month for a total of three months.

Participants burned the least number of calories following the low-fat diet, and the most following a very-low-carb regimen, similar to the high-protein Atkins diet. However, the high-protein type of diet also caused subjects to have elevated blood markers for stress and inflammation, both of which are bad for the heart, Ludwig says.

The top performer, in terms of number of extra calories burned without unhealthy side effects, turned out to be the low-glycemic diet, which helped participants burn an extra 150 calories a day.

A low-glycemic diet — some might call it a Mediterranean diet — stresses foods that are digested slowly, which helps people feel fuller longer, such as minimally processed grains, beans, vegetables, fruits, lean protein and nuts.

"The results of our study challenge the notion that a calorie is a calorie from a metabolic perspective," the researchers wrote.

Some experts caution against coming to conclusions too quickly based on the study. Charles Burant, M.D., an obesity and metabolism researcher at the University of Michigan, says that being overweight is not good for your heart and weight loss, by whatever diet, has a significant beneficial effect on health. He thinks that it's premature to suggest that one diet is better than another. "People need to find the one that works for them, both in the short term and in the long term," he says.

Similarly, Jules Hirsch, M.D., emeritus professor at Rockefeller University, told the New York Times he has done similar research on diet and weight loss and discovered that people who successfully lose weight and keep it off don't typically switch to a whole new diet. Rather, they just consume fewer calories — essentially less of what they usually eat — and, ideally, exercise more.

But Christopher Gardner, an associate professor of medicine at Stanford University, believes the study provides important new evidence about the effectiveness of different weight loss diets.

If an additional 150 calories a day could be burned following a low-glycemic diet, it may not seem like much, he says, but over time, that would add up to serious weight loss.

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