Study Challenges Idea That Varying Amounts of Fat,

Protein and Carbohydrate are Key to Weight Loss


Whether you are just starting a New Year’s diet or struggling to maintain a healthy weight, a new study offers some timely guidance.  When it comes to accumulating body fat, it isn’t so much what you eat, but how much you eat that counts.  The findings are the latest in a string of studies that challenge claims that the secret to weight loss lies in adjusting the amount of nutritional components of a diet—protein, fat and carbohydrate.

The diet industry has offered dozens of strategies recommending raising or lowering carbohydrates, protein or fat.  In the study, published in the January 11, 2012 issue of The Journal of the American Medical Association, 25 young, healthy men and women were deliberately fed nearly 1,000 excess calories per day for 56 days, but with diets that varied in the amounts of protein and fat.   While those on a low-protein diet—about 5% of total calories—gained less weight than those on a normal-or-high-protein regimen, body fat among participants in all three groups increased by about the same amount.  Typical protein consumption is about 15% of calories, while the U.S. government recommends it make up between 17-21% of total calories.

The findings suggest that it matters little whether a diet is high or low in fat, carbohydrate or protein; it’s calories that build body fat.  Weight gain depends primarily on excess calories, regardless of the composition of the meal.  More than 60% of U. S. adults are considered overweight and more than 30% are obese, defined as having a body mass index, or BMI, of 30 or higher. 

There was a potentially detrimental effect of the low-protein diet: Participants had a reduction in the levels of lean body mass.  Those whose diet was 15% or 25% protein had an increase in lean body mass, a reason that they gained more weight than those on a low-protein diet.  And there is no health-related benefit to a reduction in lean body mass.   BMI, a calculation based on height and weight, is widely used to describe the weight status of a population.  But it is increasingly controversial when used to assess the health of individual patients.  The fact that patients in the study gained less weight on a low-protein diet but still accumulated substantial body fat suggests relying on BMI measurement may be misleading patients and doctors about obesity risk.  The editorial accompanying the study urges clinicians to focus on fat reduction rather than simply weight loss when treating obese patients.

Source: Ron Winslow and The Wall Street Journal