Effect of weight loss and exercise therapy on bone metabolism and mass in obese older adults: A one-year randomized controlled trial

Background: Although weight loss and exercise ameliorates frailty and improves cardiac risk factors in obese older adults, the long-term effect of lifestyle intervention on bone metabolism and mass is unknown. Objective: The objective was to evaluate the effects of diet-induced weight loss in conjunction with exercise on bone metabolism and mass in obese older adults. Design and Setting: We conducted a one-year randomized, controlled clinical trial in a university-based research center. Participants: Twenty-seven frail, obese (body mass index = 39 +/- 5 kg/m(2)), older (age 70 +/- 5 yr) adults participated in the study. Intervention: Participants were randomly assigned to diet and exercise (treatment group; n = 17) or no therapy (control group; n = 10). Outcome Measures: Body weight decreased in the treatment group but not in the control group (-10 +/- 2 vs. +1 +/- 1%, P < 0.001). Compared with the control group, the treatment group had greater changes in bone mass, bone markers, and hormones, including 1) bone mineral density (BMD) in total hip (0.1 +/- 2.1 vs. -2.4 +/- 2.5%), trochanter (0.2 +/- 3.3 vs. -3.3 +/- 3.1%), and inter-trochanter (0.3 +/- 2.7 vs. -2.7 +/- .3.0%); 2) C-terminal telopeptide (12 +/- 35 vs. 101 +/- 79%) and osteocalcin (-5 +/- 15 vs. 66 +/- 61%); and 3) leptin (2 +/- 12 vs. -30 +/- 25%) and estradiol (0.1 +/- 14% vs. -14 +/- 21%) (all P < 0.05). Changes in weight (r = 0.55), bone markers (r = -0.54), and leptin (r = 0.61) correlated with changes in hip BMD (all P < 0.05). Conclusion: Weight loss, even when combined with exercise, decreases hip BMD in obese older adults. It is not known whether the beneficial effects of weight loss and exercise on physical function lower the overall risk of falls and fractures, despite the decline in hip BMD.