Higher sedentary energy expenditure in patients with Huntington's disease

Weight loss is common among patients with Huntington's disease (HD), although the mechanisms contributing to this phenomenon are not known. We measured 24-hour sedentary energy expenditure (24-hour EE) and sleeping metabolic rate (SMR) in a human respiratory chamber in 17 patients with mild to moderate HD and 17 control subjects matched for age, sex, and body mass index. Total energy expenditure was measured during 7 days in free-living conditions, using the doubly labeled water technique. Body weight, fat mass, and fat-free mass (measured by dual-energy x-ray absorptiometry) were similar in patients with HD and control subjects. Twenty-four-hour EE was 14% higher in HD patients than controls in absolute terms (2,038+/-98 vs 1,784+/-68 kcal/24 hours) and after adjustment for age, sex, fat mass, and fat-free mass (1,998+/-45 vs. 1,824+/-45 kcal/24 hours). In contrast, SMR and total energy expenditure were similar in patients and controls both in absolute terms (1,314+/-38 vs 1,316+/-42 and 2,402+/-102 vs. 2,373+/-98 kcal/24 hours, respectively) and after adjustment. Spontaneous physical activity measured by radar in the chamber and the ratio of 24-hour EE to SMR were significantly higher in HD patients than controls (11.4+/-1.4 vs 6.1+/-0.6% and 1.54+/-0.05 vs 1.36+/-0.03, respectively). In the group as a whole, 24-hour EE/SMR correlated with spontaneous physical activity. Among HD patients, both 24-hour EE/SMR and spontaneous physical activity correlated with the severity of chorea, but SMR and total energy expenditure did not. There were no differences in reported energy intake during 7 days in patients with HD compared with controls. The results of this study indicate that sedentary energy expenditure is higher in patients with HD than in controls in proportion to the severity of the movement disorder. Total free-living energy expenditure is not higher, however, because patients with HD appear to engage in less voluntary physical activity.