INCREASED ENERGY-EXPENDITURE ASSOCIATED WITH REPETITIVE INVOLUNTARY MOVEMENT DOES NOT CONTRIBUTE TO GROWTH FAILURE IN GIRLS WITH RETT-SYNDROME

Objective: To determine whether increased total daily energy expenditu re (TDEE) associated with repetitive, involuntary movements contribute s to growth failure in girls with Rett syndrome (RS), Study design: Fo urteen girls with RS and 11 healthy girls were studied for 10 days to obtain measurements of height, weight, body circumference, and skin-fo ld thickness with stadiometric and anthropometric methods; whole-body potassium by potassium 40 counting; 72-hour dietary energy intakes bg test weighing; 24-hour activity patterns using observational methods; and TDEE using the doubly-labeled water technique, Results: TDEE, when adjusted for differences in lean body mass, did not differ significan tly between girls with RS and healthy girls. Although, girls with RS s pent more waking hours in physical activity than their healthy counter parts (85% +/- 10% vs. 73% +/- 11% awake time per day, p < 0.05), thei r repetitive movements were not sufficiently intense to increase TDEE. However, girls with RS had significantly less lean body mass, but not body fat, which contributed to their lower absolute TDEE in compariso n with that of healthy girls (845 +/- 251 vs. 1453 +/- 534 kcal/day, p < 0.01), Dietary energy intake, when adjusted for differences in body weight, was not significantly different in girls with RS compared wit h healthy girls. Conclusions: Increased TDEE as a result of repetitive , involuntary movements does not explain the alterations in growth and body composition of girls with RS.