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 expenditure (TDEE) associated with repetitive, involuntary movements contributes to growth failure in girls with Rett syndrome (RS).

STUDY DESIGN

Fourteen girls with RS and 11 healthy girls were studied for 10 days to obtain measurements of height, weight, body circumference, and skin-fold thickness with stadiometric and anthropometric methods; whole-body potassium by potassium 40 counting; 72-hour dietary energy intakes by 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 significantly between girls with RS and healthy girls. Although girls with RS spent more waking hours in physical activity than their healthy counterparts (85%+/-10% vs. 73%+/-11% awake time per day, p < 0.05), their 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 comparison 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 with 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.