Abstracts Womens Studies

Effects of weigh-bearing and non-weight bearing exercise on markers of bone turnover during short-term weigh loss in overweight premenopausal women

by Joanne V. Loethen

Moderate weight reduction is associated with loss of bone mass in overweight women. The purpose of this study was to evaluate the effects of weight-bearing and non-weight bearing exercise on markers of bone formation and bone breakdown during short-term weight loss in overweight, premenopausal women (n=37). Participants lost 5% of their initial body weight in 6 wk via: caloric restriction alone (DIET, n=11), plus non-weight bearing aerobic exercise (CYCLE, n=12), or plus weight-bearing aerobic exercise (RUN, n=13).Serum markers of bone turnover and hormones were measured before and after weight loss. Repeated measures two-way ANOVA was used to test for time and group effects, and group-by-time interactions. DIET, CYCLE, and RUN groups did not differ at baseline in age, body weight, or BMI. Body weight and BMI decreased significantly in all groups from baseline to post-weight loss (p [less than] 0.05). Osteocalcin (OC), a formation marker, increased significantly (9%) with weight loss in all groups (p [less than] 0.05). C-terminal cross-links of type I collagen (CTX) and bone-alkaline phosphatase (BAP) did not change in any of the groups. Leptin decreased significantly with weight loss in all groups (59.1%, p [less than] 0.001), but no significant main effects or interactions were observed for 25OH-D, IGF-1, fT3, or iPTH. Markers of bone formation increased in response to weight loss and the weight-bearing aerobic exercise included in this study may not have been of sufficient duration or intensity to override the acute effects of weight loss on markers of bone turnover.