contribution of body composition and activity behaviors to variation of total energy expenditure in pre-school children

ba ckground: although it is widely accepted that the pre-school age is a critical period  in  the  development of  obesity,  there  are  few  published data  on  factors contributing to variation of total energy expenditure in this age group.to investigate the contribution of body composition, gender and activity on total energy expenditure (tee) in pre-school children. m ethods: the total energy expenditure of 89 children (2-6 years old) was measured using  the doubly  labelled  water  (dlw)  technique.  total  and  regional  body composition were also measured using deuterium dilution and dual energy x-ray absorptiometry (dxa) respectively. physical activity and sleep patterns were evaluated using an accelerometer. principal components analysis (pca) were performed on regional fat mass (fm), regional fat free mass (ffm) and behavioural variables (activity, inactivity and sleep patterns), to generate orthogonal predictors for regression analyses. results: no significant difference was found between boys and girls for, log weight, height, bmi sds, total ffm and log fm measured by dxa and total ffm and log obtained with deuterium dilution. no significant gender difference was found for regional traits of ffm and fm except for trunk’ ffm (p=0.02) and legs’ ffm (p=0.04), which were higher in boys.  ffm and fm measured by dxa explained 70.9% of the variation in tee, and tee was significantly lower amongst girls after adjustments for body composition were made (p<0.01). the first component of ffm (pc1-ffm), fm (pc1-fm) and behavioural variables (pc1-bv) were positively (p<0.01) related to tee and there was a significant negative relationship with pc2- fm (p<0.05) and pc4-bv (p<0.01). conclusion: most variation in tee in this group was explained by difference in ffm and fm. behavioural factors, particularly time spent in high activities could make an additional contribution of 20.9% in variation of free-living tee. more research is needed to confirm these findings in other population.