URBANA, Ill.—Postmenopausal women who are trying to lose weight to improve their quality of life should increase their dietary intake of protein to increase satiety and preserve muscle mass, according to a study published in the Journal of Gerontology.
Researchers at the University of Illinois conducted a 6-month double-blind study of 31 healthy, postmenopausal obese women who were divided into two groups. Each group followed a 1,400-calorie weight-loss diet based on USDA's My Pyramid, but one group received a powdered whey protein supplement in the morning and again in the afternoon or evening; the other received a placebo that contained carbohydrates.
Both groups were encouraged to engage in light exercise (walking and stretching) and given diet education, including examples of healthy daily menus and a scale to measure portion size. Before and after the study, participants were assessed for strength, balance, and the ability to perform such physical tasks as walking 50 feet, standing up five times from a chair, and lifting a book 12 inches above shoulder height. Magnetic resonance imaging (MRI) was used at the beginning and end of the study to measure muscle volume of the right thigh, the amount of fat around the thigh, and the amount of fat within the thigh muscle.
The study found higher protein intake during weight loss can offset negative effects on muscle mass by maintaining more muscle relative to the amount of weight lost. Women who ate more protein lost 3.9% more weight and had a relative gain of 5.8% more thigh muscle volume than woman who did not.
In both groups, strength decreased as weight decreased. However, the study suggests that an increase in the amount of muscle relative to fat had beneficial effects on balance and performance. Even though weight loss in these older women had a negative effect on strength, their reduced weight helped with other aspects of physical function.
