ENERGY-REQUIREMENTS FROM INFANCY TO ADULTHOOD

To investigate how age and body composition affect energy requirements , the sedentary daily expenditure (SDE) and basal metabolic rate (BMR) of 101 infants, 82 girls, and 27 adults were measured. Energy expendi ture was scaled for differences in body size to test the effects of ag e and body fatness. A power function was superior to linear models. Fo r all subjects, WT0.63 (where WT is weight) or FFM(0.63) (where FFM is fat-free mass) explained 94% of the variability in BMR, and WT0.70 Or FFM(0.70) explained 97% of the variability in SDE. The effects of hei ght and fat mass (kg or % body wt) on BMR and SDE scaled for weight or fat-free mass were age dependent. Best-fitted exponents relating BMR or SDE to body size differed between children (0.40-0.52) and infants (1.04-1.30) (P = 0.001). Human energy requirements from infancy to adu lthood appear to be a power, not a linear, function of body weight and composition.