The age-old advice to eat less and move more to lose weight still holds true, but new research revealed that cutting calories is equally as effective as a combination of diet and exercise -- as long as the calories consumed and burned are equal.
The new study published in the Journal of Clinical Endocrinology & Metabolism also found that adding exercise to a weight-loss regimen does not improve body composition and abdominal fat -- debunking the myth that specific exercises can target belly fat and trim the waistline.
Researchers at Pennington Biomedical Research Center at Louisiana State University in Baton Rouge set out to explore the benefits of diet plus physical activity compared to calorie restriction alone.
They wanted to test the hypothesis that adding exercise to a reduced-calorie diet would improve metabolic risk factors, such as changes in abdominal fat distribution.
Fat stored around the abdomen and waist is considered the most dangerous type of fat. This so-called central obesity increases the risk of heart disease, diabetes and insulin resistance.
To test the impact of various approaches on reducing abdominal fat, researchers closely followed 35 overweight but otherwise healthy men and women for six months.
Participants were randomly assigned to one of three groups. One group ate a reduced-calorie diet designed to be 25 percent less than normal, which equated to between 550 and 900 fewer calories per day.
A second group followed a plan that combined diet and exercise. They ate 12.5 percent fewer calories and increased their physical activity to achieve an additional 12.5 percent increase in calorie expenditure.
The final group acted as the control group. They followed a diet plan designed to maintain their body weight.
During the first three months of the study, participants were provided with all of their meals. Afterwards, participants were monitored by researchers, but allowed to select their own diet based on their individual calorie target.
After the six-month study period, both the calorie-restricted group and the exercise group lost similar amounts of weight and fat -- about 10 percent of their body weight and 24 percent of their fat mass. There was little difference between the two groups.
"It's all about the calories," said lead author Dr. Leanne Redman in a telephone interview. "A calorie deficit achieved through diet or an increase in exercise had the same effect on body composition."
But Redman said the most "interesting part of the results" was the lack of changes in fat distribution. Neither group experienced a reduction in abdominal fat, suggesting that genetics may be playing a powerful role.
"Our bodies may be genetically programmed to store or burn fat in a certain way and diet or exercise couldn't alter that."
The finding also reinforced the concept that "spot reducing" is not effective. No type of exercise can specifically melt fat around the midsection.
So what does this all mean? Is exercise a secondary or less significant factor in weight control? Fat chance.
Even though the increased physical activity did not budge belly fat -- it did improve the aerobic fitness level of the exercise group compared to the calorie-restricted and control groups.
The authors concluded that aerobic fitness has other important cardiovascular and metabolic implications.