IMPACT OF WEIGHT LOSS AND AEROBIC EXERCISE ON NUTRITION AND BONE MINERAL DENSITY IN AFRICAN AMERICAN AND CAUCASIAN POSTMENOPAUSAL WOMEN.

Background: Weight loss is often recommended for obese women to reduce fat mass and the risk of developing chronic diseases, but may result in a reduction of bone mineral density (BMD). African Americans have greater BMD than Caucasians, but differences in the decrease in BMD between these races following weight reduction with and without exercise are unknown.

Objectives: The purpose of this study was to investigate the hypothesis that Caucasian women would lose greater amounts of BMD than African American women after undergoing weight loss, but that the addition of aerobic exercise would attenuate the loss in both races.

Design: Longitudinal.

Participants: African American (n=34) and Caucasian (n=63), overweight and obese postmenopausal (age 45-80 years).

Intervention: Six months of weight loss (250-350 kcal/days deficit) alone (WL) or in combination with aerobic exercise consisting of 3 days/week treadmill training at >85% of heart rate reserve for 45 min (AEX+WL).

Measurements: Femoral neck, total femur, and lumbar BMD, VO2max, urinary calcium, and dietary intake.

Results: African American women had a greater body weight, BMI, and BMD all sites and lower dietary protein and calcium intakes than Caucasian women (all P<0.05). Weight decreased 7.5% in both groups and VO2max increased only after AEX+WL (intervention effect, P<0.001). Both races lost ~1% of their femoral neck and total femur BMD following the interventions (P's<0.01). There were no race by intervention interactions. There was a trend for the women undergoing WL to lose greater femoral neck BMD than those in AEX+WL (P=0.07). There were no associations between changes in BMD and changes in VO2max, urinary calcium, or dietary intake.

Conclusions: Our data indicate that despite beginning the interventions with greater BMD than Caucasian postmenopausal women, African Americans were not spared from losses of femoral neck and total femur BMD following six months of weight loss, but that addition of aerobic exercise to weight loss tends to attenuate the decreases in femoral neck BMD in both races.