Activity Energy Expenditure And The Change In Body Composition During Late Life

Abstract

Change in body composition, specifically loss of lean and gain in fat mass in older adults is a major pathway leading to the onset of functional decline. Energy expenditure during daily activity may help preserve body weight and composition among older adults. PURPOSE: To determine the association of activity-related energy expenditure and change in body weight and composition among older adults. METHODS: Total energy expenditure (TEE) was assessed over two weeks using doubly-labeled water in 302 community dwelling older adults (aged 70 to 82 years). Resting metabolic rate (RMR) was measured using indirect calorimetry and the thermic effect of meals was estimated at 10% of TEE. Activity energy expenditure (AEE) was calculated as: [TEE(0.9)-RMR] and categorized into gender specific equal thirds (tertiles). Total body mass, lean mass and fat mass were assessed by dual-energy x-ray absorptiometry annually over an average of 4.8 years. RESULTS: At baseline, individuals in the highest tertile of AEE were heavier (79.6 ± 16.5 kg) than those in the lowest tertile (72.8 ± 15.3 kg), but not the middle tertile (76.6 ± 14.4 kg). Consequently, higher levels of AEE were also associated with greater lean (r = 0.13, p = 0.02) and fat mass (r = 0.12, p = 0.03). In longitudinal analyses, person-specific paths of the change in body weight estimated from a random-effects model demonstrated a significant decline in body weight (−0.38 kg/yr, p<0.001) that was consistent across all AEE tertiles (tertile 1: −0.42 ± 0.62; tertile 2: −0.29 ± 0.60; tertile 3: −0.42 ± 0.70 kg/yr). Similarly, lean mass declined by 0.28 kg per year (p<0.001) regardless of AEE levels (tertile 1: −0.28 ± 0.31; tertile 2: −0.27 ± 0.26; tertile 3: −0.31 ± 0.31 kg/yr). Total fat mass remained stable over the follow-up (β = −0.035 kg/yr, p = 0.43) and AEE levels did not affect this trajectory (p>0.20). Results were similar when values were adjusted for baseline and longitudinal changes in total body weight. CONCLUSIONS: These data suggest that although AEE has a concurrent association with body weight and composition in late life, higher levels of AEE does not appear to impact the trajectory of change. Supported by N01-AG-6-2101, N01-AG-6-2103, N01-AG-6-2106 and in part by the Intramural Research Program of the NIH, National Institute on Aging.