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January 15, 1999 African American Women and Weight Loss Lower Metabolic Rates May Make It Harder to Take It Off and Keep It Off Millions of Americans have made New Year's resolutions to lose weight in 1999. Unfortunately, most of these dieters will not reach their goals. Part of the reason may be metabolic, especially for African American women. It was already known that, before weight loss, overweight black women burned fewer calories at rest than did white women. A new study by researchers at the University of Pennsylvania School of Medicine is the first to show that after weight loss, black women experience greater drops in metabolic rate than do white women. This finding, published in this month's American Journal of Clinical Nutrition, lends further support to the idea that biological factors may be partly responsible for the consistent finding that black women tend to lose less weight than white women in weight control programs. Investigators measured the resting metabolic rate of 109 (24 black, 85 white) overweight women (average of 211 pounds) before and after a six-month weight loss program. The resting metabolic rate is the number of calories burned at rest, and makes up two-thirds of all the energy burned in one day. Consistent with previous findings, before weight loss, black women burned 103 fewer calories than white women of similar weights and body composition. The new finding reports that after weight loss, the resting metabolic rate of black women dropped 10 percent (171 calories) compared to 6 percent (109 calories) for white women, despite the fact that black women lost less weight (29 lbs.) than white women (36 lbs.). "This double whammy presents very real biological barriers against weight loss in African American women," says Gary D. Foster, Ph.D., clinical director of the Weight and Eating Disorders Program at the University of Pennsylvania Medical Center. "And physicians need to be sensitive to this fact and not just assume that someone isn't trying hard enough or not following recommendations." Although lower metabolic rates may make weight control more difficult, Foster cautions against abandoning all efforts. "We hope that these findings can help overweight black women and their doctors set realistic expectations for weight loss. Changes in diet and activity will lower weight and improve health among African American women. However, there may be biological limits to how much weight loss can be reasonably achieved," adds Foster.