Fewer Calories Or More Exercise: The Effect On Body Composition Is Identical

New research published in the Journal of Clinical Endocrinology & Metabolism reveals that dieting alone is equally effective at reducing weigh and fat as a combination of diet and exercise--as long as the calories consumed and burned equal out. The research also indicates that the addition of exercise to a weight-loss regimen does not change body composition and abdominal fat distribution, debunking the idea that specific exercises can reduce fat in targeted areas (e.g., exercise to reduce fat around a person's midsection).

"It's all about the calories," said Dr. Eric Ravussin of the Pennington Biomedical Research Center in Baton Rouge, La., and senior author of the study. "So long as the energy deficit is the same, body weight, fat weight, and abdominal fat will all decrease in the same way."

Other researchers on the Pennington Biomedical Research Center team include Drs. Leanne M. Redman, Leonie K. Heilbronn, Corby K. Martin, Anthony Alfonso, and Steven R. Smith.

For the study, the researchers followed 35 overweight (a Body Mass Index greater than 25 but less than 30) but otherwise healthy adults who were randomly assigned to follow one of three diet and exercise combinations during a six-month period. The first group was the control group, and followed a healthy diet designed to maintain the participants' bodyweight. The next group followed a diet that reduced their caloric intake by 25 percent, which equaled between 550 and 900 fewer calories per day. The final group reduced their calorie intake by 12.5 percent while increasing their physical activity to achieve an additional 12.5 percent increase in calorie expenditure.

"It was critical for our study that the calorie deficit for both groups--the one following the diet and exercise regimen and the one simply consuming fewer calories--be equal," said Ravussin. "This ensured that we would be able to measure the impact of exercise on body composition and abdominal fat."

The study began with a 5-week baseline period to carefully establish individual energy requirements. During this time, the researchers calculated the energy intake required for weight maintenance and the energy deficit necessary to achieve the desired caloric restriction.

During the first three months of the study, participants were provided with all meals. Later, participants self-selected a diet based on their individual calorie target, though calorie consumption was still monitored. Participants in the exercise group also underwent a structured exercise regimen 5 days a week. In addition to controlling diet and a guided exercise program, all participants attended weekly meetings to not only teach subjects how to adhere to their meal and exercise plans but also to boost motivation and morale.

Participants in both the calorie restricted group and the exercise group lost approximately 10 percent of their body weight, 24 percent of their fat mass, and 27 percent of their abdominal visceral fat. The distribution of the fat in the body, however, was not altered by either approach.

"The inability of the interventions to alter the distribution of fat suggests that individuals are genetically programmed for fat storage in a particular pattern and that this programming cannot easily be overcome," said Ravussin. "It also helps settle much of the debate over the independent and combined effects of dieting and increased physical activity on improving metabolic risk factors such as body composition and fat distribution."

The researchers did note, however, that exercise improved aerobic fitness, which has other important cardiovascular and metabolic implications. "For overall health, an appropriate program of diet and exercise is still the best," said Ravussin.

The researchers also acknowledge that additional research is necessary to investigate in a large number people all the independent health benefits of calorie restriction and exercise.

Pennington Biomedical Research Center is a campus of the Louisiana State University System.

The Journal of Clinical Endocrinology & Metabolism is a publication of The Endocrine Society.

Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones, and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 13,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Maryland.

An online, Rapid Release version of the paper, "Effect of calorie restriction with or without exercise on body composition and fat distribution," was published January 2, 2007. The final paper will appear in the March 2007 issue of the Journal of Clinical Endocrinology & Metabolism.