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

Although it is widely accepted that the pre-school age is a criticalperiod in the development of obesity, there are few published data on factorscontributing to variation of total energy expenditure in this age group.To investigate the contribution of body composition, gender and activity on totalenergy expenditure (TEE) in pre-school children. The total energy expenditure of 89 children (2-6 years old) was measuredusing the doubly labelled water (DLW) technique. Total and regional bodycomposition were also measured using deuterium dilution and dual energy X-rayabsorptiometry (DXA) respectively. Physical activity and sleep patterns wereevaluated using an accelerometer. Principal components analysis (PCA) wereperformed on regional fat mass (FM), regional fat free mass (FFM) and behaviouralvariables (activity, inactivity and sleep patterns), to generate orthogonal predictorsfor regression analyses. 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 logobtained with deuterium dilution. No significant gender difference was found forregional 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 explained70.9% of the variation in TEE, and TEE was significantly lower amongst girls afteradjustments 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). Most variation in TEE in this group was explained by difference inFFM and FM. Behavioural factors, particularly time spent in high activities couldmake an additional contribution of 20.9% in variation of free-living TEE. Moreresearch is needed to confirm these findings in other population.