Effect of an 18-month Physical Activity and Weight Loss Intervention on Body Composition in Overweight and Obese Older Adults

Objective: Our primary objective was to determine the long-term effects of physical activity (PA) and weight loss (WL) on body composition in overweight/obese older adults. Secondarily, the association between change in body mass and composition on change in several cardiometabolic risk factors and mobility was evaluated.

Design And Methods: 288 older (X ± SD: 67.0 ± 4.8 years), overweight/obese (BMI 32.8 ± 3.8 kg/m² ) men and women participated in this 18-month randomized, controlled trial. Treatment groups included PA + WL (n = 98), PA-only (n = 97), and a successful aging (SA) health education control (n = 93). DXA-acquired body composition measures (total body fat and lean mass), conventional biomarkers of cardiometabolic risk, and 400-m walk time were obtained at baseline and 18 months.

Results: Fat mass was significantly reduced from (X ± SE) 36.5 ± 8.9 kg to 31.7 ± 9.0 kg in the PA + WL group (p < 0.01), but remained unchanged from baseline in the PA-only (-0.8 ± 3.8 kg) and SA (-0.0 ± 3.9 kg) group. Lean mass losses were three times greater in the PA + WL groups compared to PA-only or SA groups (-2.5 ± 2.8 kg vs. -0.7 ± 2.2 kg or -0.8 ± 2.4 kg, respectively; p < 0.01); yet due to a larger decrease in fat mass, percent lean mass was significantly increased over baseline in the PA + WL groups (2.1% ± 2.6%; p < 0.01). Fat mass loss was primarily responsible for WL-associated improvements in cardiometabolic risk factors, while reduction in body weight, regardless of compartment, was significantly associated with improved mobility.

Conclusion: This 18-month PA + WL program resulted in a significant reduction in percent body fat with a concomitant increase in percent body lean mass. Shifts in body weight and composition were associated with favorable changes in clinical parameters of cardiometabolic risk and mobility. Moderate PA without WL had no effect on body composition.