Background: Children with Down syndrome (DS) have a higher prevalence of obesity than other children. Whether this increased risk for obesity is due to a lower resting energy expenditure (REE) is controversial. Our study assessed whether (1) the REE of children with DS adjusted for fat-free mass (FFM) was lower than that of sibling controls, and (2) the changes in fat mass (FM) over 3 years were associated with FFM-adjusted baseline REE.
Methods: This study used cross-sectional and prospective cohort designs. Four annual measurement visits were conducted with 28 children with DS and 35 sibling controls aged 3-10 years. REE and serum thyroxine (T4) were measured at baseline. Anthropometry, skinfold thickness measures, and, in a subsample, dual-energy x-ray absorptiometry (DXA) were used at each visit to calculate FM.
Results: Children with DS had significantly lower REE adjusted for FFM (-78 kcal/day, 95% CI: -133 to -27, P=0.003). The difference remained significant after adjustment for FM, sex and African ancestry (-49 kcal/day, 95% CI: -94 to -4, P=0.03). In the longitudinal analysis, the baseline REE adjusted for baseline FFM was not predictive of FM accretion over time (P=0.8).
Conclusion: Children with DS have lower REE than sibling controls, but REE was not associated with changes in FM over time. The results suggest that the lower REE of children with DS does not explain their increased risk for obesity.