PHYSICAL-ACTIVITY RELATED ENERGY-EXPENDITURE AND FAT MASS IN YOUNG-CHILDREN

OBJECTIVE: To examine whether body fat content in pre-pubertal childre n is influenced by physical activity related energy expenditure (AEE) and/or more qualitative aspects of physical activity. DESIGN: Cross-se ctional study. SUBJECT: 101 pre-pubertal children were examined in Stu dy 1: (age: 5.3 +/- 0.9 y; weight: 20.2 +/- 3.6 kg). In Study 2: 68 of the original children were re-examined (age: 6.3 +/- 0.9 y; weight: 2 3.6 +/- 5.0 y). MEASUREMENT: Fat mass (FM) and fat free mass (FFM) wer e determined by bioelectrical resistance and skinfolds; AEE was estima ted from the difference between total energy expenditure (TEE) by doub ly labeled water and post-prandial resting energy expenditure (REE) by indirect calorimetry; qualitative information on activity was derived by questionnaire. RESULTS: AEE was significantly correlated with FFM (r = 0.32 in both Studies) and body weight (r = 0.28 in Study 1; r = 0 .29 in Study 2), but not FM. There were no significant relationships b etween AEE and any of the variables from the activity questionnaire in children (including TV time, playing time, and an accumulated activit y index in h/week). After adjusting for FFM, age, and gender, FM was i nversely related to activity time in h/week (partial r = -0.24 in Stud y 1; partial r= -0.32 in Study 2) but not AEE (P > 0.5). CONCLUSION: A fter adjusting for FFM, age, and gender, a small portion of the varian ce in body fat mass in children (similar to 10%) is explained by time devoted to recreational activity, whereas none of the variance is expl ained by the combined daily energy expenditure related to physical act ivity.