January 30, 2006

Research Study Reveals a Protein-rich Diet Boosts Benefit of Exercise

URBANA--Weight gain and obesity rates have become an epidemic problem in Illinois and throughout the nation. At least 3.6 million adult Illinois residents--66% of men and 57% of women--are categorized as obese and healthcare costs associated with obesity approach $700 million annually (Illinois Department of Public Health).

Research funded by the State of Illinois via the Illinois Council on Food and Agricultural Research (C-FAR) may help consumers lose excess weight and improve their overall health. A research study led by Donald Layman, a professor of food science and human nutrition at the University of Illinois at Urbana-Champaign, demonstrated that a weight-loss program is more effective when it combines exercise with a protein-rich diet. "There's an additive, interactive effect when a protein-rich diet is combined with exercise. Dieters lose more weight, and they lose fat, not muscle," said Layman. "A higher-carbohydrate, lower-protein diet based on the USDA food guide pyramid actually reduced the effectiveness of exercise."

Forty-eight women participated in a four-month study, eating about 1,700 calories per day. The women were divided into two groups. One group ate a diet rich in high-quality proteins such as meats, dairy, eggs, and nuts. The second group ate a diet based on the food guide pyramid, which contained more complex carbohydrates such as breads, rice, cereal, pasta, and potatoes and less protein.

"Both diets work because when you restrict calories, you lose weight. But the people on the higher-protein diet lost more weight. Some people refer to this as the metabolic advantage of a protein-rich diet," said Layman.

Each group was also divided into two levels of exercise. Dieters following the protein-rich, high-exercise program lost the most weight, and almost 100 percent of the weight lost was fat. Dieters following the high-carbohydrate, high-exercise program also lost weight, but as much as 25 to 30 percent of the weight lost was muscle. "We found the protein-rich diet actually boosts the benefit of doing exercise and protects lean muscle tissue," said Layman.

"While this protein-rich diet works for everyone, it appears to be even more effective for people who have high triglyceride levels and carry excess weight in their midsection. The diet dramatically lowered triglycerides and reduced abdominal fat, both risk factors associated with heart disease," said Layman.

"With the epidemic of obesity/overweight among all age groups, we need studies to show the most effective approaches to weight loss. Health care professionals can use this information to help individuals improve their health status," said Karen Little, C-FAR research vice chair and registered dietician.

"C-FAR research programs have been critical for us to pursue questions that are important to Illinois and agriculture that are often not priorities for national research organizations," said Layman.

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