A 12-month university study of 130 persons who ate either a USDA food pyramid-inspired high-carb diet or a diet moderately high in protein showed that members of the higher protein group lost 23 percent more weight and 38 percent more body fat than their high carb counterparts.
Researchers at the University of Illinois and Penn State University placed half the group on a USDA-based diet consisting of 55 percent carbohydrates, 30 percent fat, and 15 percent protein. The other diet was 40 percent carbohydrates, 30 percent protein, and 30 percent fat.
The study tracked participants through two phases, a four-month active weight loss phase and an eight-month post-loss maintenance phase. Participants, who were taught how to shop for and prepare meals specific to their diets, met weekly for weigh-ins and instruction.
At the end of 12 months, the average weight loss for the higher protein group was 23 percent higher than for the high carb group. But the scientists noted an even more interesting difference in body mass composition: At four months, the protein group members had lost 22 percent more body fat than their high carb counterparts. By 12 months, that figure had increased to 38 percent.
The researchers concluded that the higher protein diet, because it made participants less likely to snack or feel food cravings, helped their bodies metabolize fat more efficiently. Their resulting greater muscle mass was more efficient at burning calories, thus creating a sort of self-sustaining weight maintenance process.
The researchers also reported that the higher protein diet inspired greater compliance: 64 percent of the participants on that diet completed the year-long study versus 45 percent of persons on the high carb diet.
Besides long-term weight and body fat loss, another benefit was the lowering of triglyceride levels, according to the study. High triglycerides are a forerunner to heart disease.
However, another lipid, cholesterol, seemed unaffected by either diet. Although the food pyramid initially lowered cholesterol levels, they rose steadily afterward: by the end of the study, cholesterol levels were the same for dieters in both groups. That development led Donald Layman, the University of Illinois professor emeritus of nutrition who headed the study, to conclude that cholesterol levels may be more a function of genetics than diet.
(We should note that the study was funded by the National Cattlemen’s Beef Association, The Beef Checkoff, and Kraft Foods-all organizations that have an understandable interest in results that confirm protein’s beneficial role in weight loss. But whatever the sponsors’ hopes and expectations, the real test of this study’s conclusions will be if other scientists can duplicate them under similar conditions. If so, high protein diets will find increasing favor in the diabetes community.)