[Basal metabolism and postprandial thermogenesis in anorexia nervosa and constitutional leanness]

Body composition and energy expenditure (basal metabolic rate--BMR--and postprandial thermogenesis--PPT) were evaluated in 11 anorectic patients, 16 very lean young women and 26 control female subjects. BMR in absolute terms was severely depressed in the anorectics when compared to the other two groups (p less than 0.01). After adjustment for fat free mass BMR was significantly higher in the lean subjects than the controls (p less than 0.05). PTT was studied for 240 minutes after the ingestion of a 3.56 MJ mixed meal (16% Prot, 50% CHO and 34% Fat) in 7 anorectics, 7 lean and 8 control women. PPT was similar in the anorectics and in the controls, but lower in the lean subjects (p less than 0.05) than in the other two groups. This study shows that a sharp decline in BMR occurs in severely undernourished anorectic patients who, however, have a normal PPT. On the other hand, very lean healthy women tend to have higher BMR but a decreased thermic response to a mixed test meal.