24-HOUR ENERGY-EXPENDITURE AND ITS COMPONENTS IN PREPUBERTAL CHILDRENAS DETERMINED BY WHOLE-BODY INDIRECT CALORIMETRY AND COMPARED WITH YOUNG-ADULTS

The aim of the present study was to compare total daily and circadian variations of energy expenditure (EE) in 21 prepubescent 10-y-old chil dren (12 boys and 9 girls) and 18 23-y-old adults (9 men and 9 women) under the same conditions by using two large calorimetric chambers. Th e volunteers followed similar activity programs with four periods of e xercise on a cyclergometer. Total daily and sleeping EE adjusted for d ifferences in fat-free mass (FFM) and age were significantly higher in children than in adults by 35% and 27%, respectively (P < 0.001). EE during sleep decreased by 2% per hour in both age groups. Heart rate w as significantly higher in girls than in boys. The energy cost of cycl ing, adjusted for differences in FFM and external mechanical power, wa s not significantly different in children and adults. The differences in EE between children and adults may partly result from a higher prop ortion of internal organs in the FFM.