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Calories: Total Trumps Source When Dieting
Strict adherence to eating a certain proportion of carbs, fat, and protein may not be as effective for weight loss as strict adherence to eating fewer calories from all sources, according to a new study that compared four diet regimens.
In the Pounds Lost trial, researchers at Pennington Biomedical Research Center in Baton Rouge, Louisiana set out to study whether the composition of a weight loss diet affected the loss of lean body mass, total body fat, visceral fat, liver, or abdominal fat. Over four hundred overweight or obese men and women were randomly assigned to follow one of four diets: average protein, low fat, higher carbs; high protein, low fat, higher carbs; average protein, high fat, lower carbs; or high protein, high fat, lower carbs.
Low fat was defined as 20 percent of calories coming from fat, while the high fat diets derived 40 percent of their calories from fat. High protein diets had 25 percent of calories from protein while low protein diets were defined as 20 percent of calories from protein. Average protein was considered 15 percent of calories from protein.
All of the diets were designed to be low in saturated fat and cholesterol, high in fiber, include low-glycemic carbohydrates, and reduce intake by 750 calories per day. Each participant was offered both group and individual counseling over the two years of the study.
After six months, the people in the study had lost more than nine pounds of total body fat and five pounds of lean body mass on average, but after two years had regained some of this. Comparing all four of the diet groups, there was no difference in fat loss or muscle loss. Neither did the proportion of carbohydrate, fat, or protein affect the amount of abdominal, visceral, or liver fat lost. People were able to maintain a weight loss of nearly nine pounds at the two-year mark, including a nearly three-pound loss of abdominal fat.
According to Dr. George Bray, a researcher who worked on the study, the major predictor for weight loss was adherence. The people who adhered to their assigned diet lost more weight than those who did not.
Adherence was a problem in this study. Many of the study participants did not complete the study, and the diets of those who did stick with it weren't exactly what they were supposed to be. Researchers hoped to see two of the diet groups adhere to the average protein diet (15 percent) and the other two groups stick with the high protein diet (25 percent). However, all four groups ate about 20 percent of their calories from protein over the two years of the study.
The take home message from this study is that any "diet" can work if total calories are consistently reduced. People will be more successful at losing weight if they choose a healthy diet plan that is easy for them to adhere to for the long haul, and they stick with it.
A breakdown of the meal plans used for the four diets in this study can be located here.
The study was published online January 18, 2012 in the American Journal of Clinical Nutrition.
February 15, 2012