Leucine-Rich Diet Benefits Health, Weight Loss

URBANA, Ill.--Women consuming a high-protein diet--loaded with the amino acid leucine--may experience positive health benefits, according to research published in February's Journal of Nutrition (133, 2:411-7, 2003) (www.nutrition.org). Researchers at the University of Illinois, Urbana-Champaign, compared the merits of a protein-heavy diet to a control diet in a study involving 24 overweight women aged 45 to 56. Women either consumed 68 g/d of protein (control) or 125 g/d (high-protein diet), and both diets were similar in calorie and fat content. Both groups followed the National Cholesterol Education Program's Step 1 diet guidelines.

After 10 weeks, the control group lost an average of 15.3 pounds compared to the high-protein group's 16.6 pounds. The real difference between the two diets was seen in health markers. Both diets led to a 10-percent reduction in serum cholesterol, but the high-protein group also experienced a significant decrease in triglycerides. Women in the control group had a higher insulin response to meals, while women in the protein group experienced better glucose control, as well as a feeling of greater satiety after meals. The researchers, led by Donald Layman, Ph.D., concluded the high-protein diet had a better effect on blood lipids and glucose homeostasis, not to mention body composition (the treatment group lost more body fat and gained more muscle). They suggested high levels of protein may up the amount of dietary leucine--an amino acid linked to maintaining muscle mass and reducing body fat during weight loss.

In the same journal (133, 2:405-10, 2003), some of the same researchers conducted research supporting protein's effects on blood sugar. They reported that consuming a high-protein diet stabilized blood sugar levels.

In research published in the January Journal of Nutrition (133, 1:261S-7S, 2003), Layman discussed that while amino acids are beneficial for the breakdown of protein, a framework for leucine intake should be evaluated in regard to creating an effective weight-loss model.

Layman stated in a university press release dated Feb. 6 that protein needs should be based on body weight, not a percentage of calories consumed. In the weight-loss study, women on the high-protein diet consumed approximately .73 g/kg/d.

"Study participants [in the weight-loss protocol] following the moderately high-protein plan, which I call the `Sensible Solution,' were twice as effective in maintaining lean muscle mass," Layman said. "Muscle helps burn calories but is often compromised during weight loss." He plans to conduct a long-term study on the high-protein diet to further investigate the role of leucine in metabolic control.