Study Justifies Calorie Counting

For people looking to lose weight, paying attention to calorie intake may be just as important as noting where those calories came from, according to a recent study conducted by the Harvard School of Public Health and the Pennington Biomedical Research Center of Louisiana State University.

Though popular culture would lead many to believe that low fat diets are better than high fat diets with the same amount of calories, the study reveals that it is the number of calories that matters most.

“I think that people can really pick whatever healthy diet they like,” said Frank M. Sacks, a professor at HSPH and lead author of the study, naming Mediterranean, low-fat, and vegan diets as examples. “Our results say that these diets would work the same.”

The researchers said that these findings do not invalidate the effectiveness of any commercial diets, only that no one diet is better than another.

“The public might be confused as to what the perfect diet is, and this study suggests people should be focusing... on counting calories,” said Stephen D. Anton, a professor at the University of Florida who trained the dietitians who helped conduct the study. “It’s hard to predict how the weight loss industry will respond,”

The study, funded by the National Institutes of Health, assigned over 800 overweight adults to one of four diets, each composed of different ratios of carbohydrates, proteins, and fats.

Results from the two-year long clinical trial showed that all four diets led to clinically significant weight loss and health benefits.

Participants, who were recruited from Boston and Baton Rouge, were provided with menus developed by registered dietitians and were given daily feedback on how close their meals were to their assigned diets.

Participants could also choose to attend group sessions and learn about diet and behavioral self-management.

Results showed a positive association between group session attendance and weight-loss, an interesting point that merits further research, Sacks said.

“We’re now trying to understand the basis for...this huge difference between individual responses to the diet. Why are some people so successful at weight loss [than others], despite the same commitment?” Sacks said. “It’s an area that hasn’t been studied well.”

The researchers added that they believe their findings will leave a lasting impact on the scientific community.

“We’ve shown that any reasonable diet can provide weight loss, as long as caloric intake is reduced,” said Katherine D. McManus, Director of Nutrition at Brigham and Women’s Hospital who headed the diet intervention committee for the study. “It’s exciting—the message encourages long-term healthy eating habits.”

—Staff writer Helen X. Yang can be reached at hxyang@fas.harvard.edu.