ENERGY-REQUIREMENTS OF MIDDLE-AGED MEN ARE MODIFIABLE BY PHYSICAL-ACTIVITY

Background: Energy requirements for weight maintenance decrease with a ge. Often, this decline is not proportionately matched by reduced ener gy intake, resulting in weight gain. Objective: We hypothesized that e nergy requirements for total daily weight maintenance in healthy, sede ntary, middle-aged men would increase after regular aerobic exercise o r 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, seden tary (LS) men; 18 obese, sedentary (OS) men; and 10 male athletes of c omparable ages ((x) over bar +/- SEM: 58 +/- 1 y). Studies were done a t baseline and after 6 mo of aerobic exercise (LS men) or aerobic exer cise plus weight loss (OS men) or 3 mo of deconditioning (athletes). R esults: The interventions raised maximal oxygen uptake ((V) over dot O (2)max) by 15% in the LS men and by 13% in the OS men and decreased it by 14% in athletes tall P< 0.01), eliminating the differences among g roups 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 level s comparable with the baseline requirements of athletes and correlated with (V) over dot O(2)max (r(2) = 0.22, P< 0.0001) and fat-free mass (r(2) = 0.05, P< 0.02) across the range of (V) over dot O(2)max achiev ed by all subjects. Conclusions: Under free-living conditions, aerobic exercise eliminated the difference in weight-maintenance energy requi rements between middle-aged sedentary and athletic men, suggesting tha t energy requirements of healthy, middle-aged men are modifiable by re gular physical activity.