RESTING METABOLIC RATE IS NOT REDUCED IN OBESE INDIVIDUALS WITH DOWN SYNDROME

Abstract

Obesity is prevalent in individuals with Down syndrome (DS) and this has been partially attributed to lower resting metabolic rate (RMR) in this population. Most of these studies have used small subject numbers and have been done mostly in children. PURPOSE This study compared RMR in 22 individuals with DS to RMR in 20 non-disabled controls of similar age (DS=25.7 and C=27.4 yrs). Contributors to RMR were also evaluated. METHODS RMR was measured in the early morning after an overnight fast using a ventilated hood system. Peak aerobic capacity (VO2peak) was determined using a treadmill protocol with metabolic measurements. RESULTS Subjects with DS weighed more (82.1 vs 72.3 kg; p = .05), were shorter (1.53 vs 1.71 cm; p = .0001) but had higher BMI (34.9 vs 24.6; p = .001), and exhibited a lower VO2peak (19.5 vs 40.3 ml/kg/min; p = .0001) compared to controls. However, RMR was not different between groups (1518 vs 1516 kcal/day). Adjusting RMR for body weight did not change these findings. Yet, after adjusting for BMI controls exhibited higher RMR than subjects with DS (1629 vs 1415 kcal/day; p = .050). Since BMI can be artificially large in persons with DS due to their small stature we also adjusted for body surface area (BSA) and this analysis showed groups were no longer different. VO2peak (r=.306), body weight (r=.75), BMI (r=.366) and BSA (r=.79) were significantly correlated with RMR in the total population. For persons with DS only body weight (r=.74) BMI (.53) and BSA (r=.78) were significantly correlated with RMR. Body weight (r=.75), BSA (r=.82) and VO2peak (r=.69) were significant correlates of RMR in controls. Only BSA remained a significant predictor of RMR using stepwise regression for the total population and each subgroup. CONCLUSIONS These data show that individuals with DS do not have lower RMR than their non-disabled peers. Persons with DS exhibit appropriate RMR for their body size, expressed as BSA, indicating that the increased level of obesity in this population is likely a function lifestyle factors. Predictors of RMR vary slightly between persons with DS and controls.