All of the volunteers gained weight, regardless of which diet they followed. Those on the normal-protein diet gained about 13 pounds, and those on the high-protein diet increased their weight by about 14 pounds, but these two groups gained muscle mass while those on the low-protein diet did not.

All three groups gained about 7.7 pounds of body fat. Those on the low-protein diet gained about half as much weight, but they also lost an average of 1.5 pounds of lean body mass, and body fat accounted for about 90 percent of the extra calories stored as fat compared to a 50 percent gain in body fat for those eating the normal- or high-protein diet.

At the end of the study the volunteers who had been consuming the normal- or high-protein diets had a higher resting energy expenditure, which means they were burning more calories while their bodies were at rest. Muscle mass increases the body's ability to burn calories. Resting energy expenditure stayed the same for those who ate the low-protein diet.

Summarizing the results of the study, Dr. George Bray, chief of Pennington's Division of Clinical Obesity and Metabolism said: "Calories from fat and carbohydrate were stored as extra calories. Protein calories did not affect fat storage directly, but did increase energy expenditure and changes in lean body mass."

This small study has some large implications. The typical diet in the United States is high in fat, high in carbohydrates, and low in protein. The results of this study suggest that overeating on this type of diet can cause people to gain body fat, even if they aren't gaining a lot of weight.

The results also imply that the epidemic of obesity may be worse than statistics show since even people at lower weights can have excess body fat. Body composition -- or the make-up of a person's weight -- may be a more important indicator of health than weight as measured on a bathroom scale. Excess body fat is linked to a greater risk of chronic diseases such as type 2 diabetes, coronary artery disease, and stroke.

Also implicated in this study are the federal government's recommendations for minimum protein intake. The current minimum recommendations are 46 grams per day for females and 56 grams per day for males. These recommendations may not be high enough to maintain a person's lean body mass. In the study, at least 78 grams per day were needed to avoid the loss of muscle, something that is never a good idea. Most people probably need about 20 percent of their calories from protein each day, which is 100 grams for someone eating 2,000 calories a day.

How do you achieve a balanced diet that is high in protein and low in fat? Plan a diet that is chock full of fruits and vegetables of every color in the spectrum, and include lean protein such as the white meat of chicken and turkey, fish, eggs, low-fat milk and yogurt, and beans. Not only are these foods low in fat and high in protein, but they are packed with essential nutrients and phytochemicals. They are also low in calories so you can eat enough to fill you up and still stay within your calorie budget. And don't forget to include carbohydrates, mostly in the form of whole grains.

The study was published in the Journal of the American Medical Association.

Image: Yuri Arcurs/Shutterstock.

This article originally appeared on TheDoctorWillSeeYouNow.com, an Atlantic partner site.

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