Reductions in basal metabolic rate and physical activity contribute to hypothalamic obesity

Context: Obesity after hypothalamic damage is often severe and resistant to lifestyle changes. It is postulated that differences in basal metabolic rate (BMR) and physical activity may contribute to hypothalamic obesity (HO). Objective: Our objective was to investigate the role of energy expenditure, BMR, and physical activity in the etiology of hypothalamic obesity. Design: This was a cross-sectional study of three groups of children: those with HO, congenital hypopituitarism (CH), and simple obesity (SO). Results: A total of 47 children (HO = 18, CH = 13, and SO = 16) had BMR measured, using indirect calorimetry (Deltatrac II). A lower BMR was seen in the HO group, which remained even after adjusting for lean mass. Physical activity, assessed using triaxial accelerometry, demonstrated longer activity periods in the HO group, although the degree of activity was reduced. No significant differences were seen in calorie intake. Conclusion: Energy expenditure, rather than energy intake, has a greater role in the development of obesity after cranial tumor therapy. Reductions in BMR and physical activity, leading to a positive energy balance and weight gain despite an age-appropriate calorie intake, may contribute to hypothalamic obesity.