Energy Expenditure in Children with Prader‐Willi Syndrome During Walking

Abstract

Prader‐Willi Syndrome (PWS) is a complex genetic disorder caused by a deletion of the paternal chromosome 15. PWS is characterized by increased body fat, hypotonia, growth hormone (GH) deficiency, motor and cognitive disabilities, and hyperphagia, potentially resulting in obesity. This study measured and compared calorie expenditure while walking in PWS and controls. Participants included 8 children with PWS (7 were on GH replacement therapy; mean age = 11.1±0.8 y; body mass = 44.7±11.7 kg; body fat = 37.2±11.4 %; lean mass = 26.4±4.3 kg), 9 lean children (mean age = 9.8±2.0y; body mass = 35.4±11.3 kg; body fat = 22.2±8.6 %; lean mass = 25.5±11.6 kg), and 10 obese children (mean age = 10.6±1.1 y; body mass = 62.1±14.6 kg; body fat = 44.4±3.7 %; lean mass = 33.3±5.1 kg). Fat free mass (FFM) and body fat % were measured with dual x‐ray absorptiometry (DXA). Participants walked for three 5‐minute bouts on a treadmill at 2.0, 2.5, and 3.0 mph, with a 6‐minute seated rest period in between speeds. Expired gases were analyzed for minutes 4–5 of each speed. There were no group by time interactions for any of the variables of interest. PWS children had a higher VO2 ml/kg/min than obese children (p=0.04), but were similar to lean children (p=1.00); PWS children exhibited a greater caloric expenditure in kcal/kg/min than obese (p=0.03), but similar to lean (p=1.00). No other differences were found among the PWS and control groups during walking for VO2 when expressed in L/min or ml/FFM/min, caloric expenditure when expressed in kcal/min or kcal/FFM/min, or metabolic equivalents. The results of this study suggest that children with PWS are expending similar calories as lean controls of comparable body mass while walking. Thus, the difference in body fat does not appear to affect calories spent doing the same absolute work in PWS.