Energy requirements of middle-aged men are modifiable by physical activity

Abstract

Background: Energy requirements for weight maintenance decrease with age. Often, this decline is not proportionately matched by reduced energy intake, resulting in weight gain Objective: We hypothesized that energy requirements for total daily weight maintenance in healthy, sedentary, middle-aged men would increase after regular aerobic exercise or aerobic exercise plus weight loss to levels comparable with those in middle-aged athletes. Design: Weight-maintenance energy requirements were determined during weight stability (±0.25 kg) in 14 lean, sedentary (LS) men; 18 obese, sedentary (OS) men; and 10 male athletes of comparable ages (x̄ ± SEM: 58 ± 1 y). Studies were done at baseline and after 6 mo of aerobic exercise (LS men) or aerobic exercise plus weight loss (OS men) or 3 mo of deconditioning (athletes). Results: The interventions raised maximal oxygen uptake (V̇O2max) by 15% in the LS men and by 13% in the OS men and decreased it by 14% in athletes (all P < 0.01), eliminating the differences among groups at baseline. Body fat was reduced significantly in LS and OS men; fat-free mass decreased in OS men. Average daily energy requirements increased by 8% in LS men and by 5% in OS men (both P < 0.01) to levels comparable with the baseline requirements of athletes and correlated with V̇O2max (r2 = 0.22, P < 0.0001) and fat-free mass (r2 = 0.05, P < 0.02) across the range of V̇O2max achieved by all subjects. Conclusions: Under free-living conditions, aerobic exercise eliminated the difference in weight-maintenance energy requirements between middle-aged sedentary and athletic men, suggesting that energy requirements of healthy, middle-aged men are modifiable by regular physical activity.