Energy metabolism in sedentary and active 49- to 70-yr-old women

1 Exercise Physiology Laboratory, School of Education, The Flinders University of South Australia, Bedford Park, South Australia 5042; and 2 Energy Metabolism Laboratory, Commonwealth Scientific and Industrial Research Organization, Division of Human Nutrition, Adelaide, South Australia 5000, Australia This study examined differences between long-term exercising (LE) and long-term nonexercising (LNE) women [ n = 24; age 56.4 ± 6.2 (SD) yr] for resting metabolic rate (RMR) and energy expenditure in the free-living state by using doubly labeled water (DLW). There was a statistically significant difference ( P = 0.0002) between the 12 LE (94.85 ± 8.44 kJ · kg 1 · day 1 ) and 12 LNE (81.16 ± 6.62 kJ · kg 1 · day 1 ) for RMR, but this difference was only marginally significant ( P = 0.06) when the data (MJ/day) were subjected to an analysis of covariance with fat-free mass as the covariate. The DLW data indicated that the eight most active LE (12.99 ± 3.58 MJ/day) expended significantly ( P = 0.01) more energy than did the eight least active LNE (9.30 ± 1.15 MJ/day). Energy expenditures ranged from 7.64 to 18.15 MJ/day, but there was no difference ( P = 0.96) between the LE and LNE in energy expenditure during activity that was not designed to either improve or maintain fitness. These cross-sectional data on 49- to 70-yr-old women therefore suggest that 1 ) aerobic-type training results in a greater RMR per unit of body mass and also when statistical control is exerted for the effect of the metabolically active fat-free mass, 2 ) there is a large range in the energy intake necessary to maintain energy balance, and 3 ) aerobic training does not result in a compensatory reduction in energy expenditure during the remainder of the day. resting metabolic rate; doubly labeled water