Increase in diet-induced thermogenesis at the start of refeeding in severely malnourished anorexia nervosa patients.

Many reports describe the difficulty for anorexia nervosa patients to gain weight during refeeding. To assess whether an increase in diet-induced thermogenesis (DIT) participates to this resistance, we studied DIT by indirect calorimetry in 11 severely malnourished anorexia nervosa patients [body mass index (BMI; in kg/m2) = 13] to accomplish two purposes: 1) to compare DIT in a strict semistarvation state with that obtained after 1 wk refeeding, when metabolism is shifted to a dynamic trend toward regaining weight, without significant change in body composition; 2) to study the effect on DIT of two energetic loads representing each one-third of the energy intake during semistarvation and refeeding, respectively: 1.25 and 2.92 MJ. To avoid bias, the two liquid loads were infused intragastrically in a random double-blind fashion. A significant increase in DIT during refeeding was observed for the two loads (204 +/- 23 kJ for the 1.25-MJ liquid meal and 482 +/- 78 kJ for the 2.92-MJ one, P < 0.02). The higher the load, the larger the increase with refeeding (P < 0.001). This increment in DIT exceeded the increase in active lean body mass and was poorly correlated with lean body mass. These results provide clear evidence of a strong cellular "waste" mechanism in anorexia nervosa patients during the early phase of refeeding, which enhances the adaptative resistance to overfeeding that we have already shown for resting energy expenditure.