Objectives: In patients with anorexia nervosa (AN), weight gain is lower than that expected from the energy content of the meals. Thus we investigated the thermic effect of food (TEF) in relation to subjective feelings and plasma hormone levels in a group of AN patients.

Methods: TEF, feelings (14 items) and plasma release of beta-endorphin, ACTH, cortisol, dopamine and catecholamines were evaluated in 15 AN patients (BMI: 13.6 ± 1.2 kg.m^-2) and in 15 healthy women after 3 gastric loads (0, 300, 700 kcal) infused by a nasogastric tube in a blind design.

Results: In AN, the blind loads induced an energy-dependent increase in TEF (P < 0.001), which was higher than that observed in healthy women (P < 0.001). Only in AN, a load-dependent decline in the high basal plasma level of -endorphin (P < 0.01), an increase in plasma ACTH (P < 0.02) after the two caloric loads and an increase in cortisol, norepinephrine and dopamine levels after the 700-kcal load only (P < 0.05) were noted. A calorie-dependent (P < 0.001) increase in nausea, abdominal discomfort and fear to being fat ratings and a decrease in liking to eat eating (P < 0.001) and body image were observed in AN patients (P < 0.05). TEF correlated with ratings on satiation, nausea, uncomfortable abdominal swelling, body image and fear to being fat (for all, P<0.01).

Conclusion: In AN women, blindly-infused loads induced a dose-dependent increase in TEF which correlated with the increase in plasma cortisol, ACTH and catecholamines as in unpleasant sensations, fear to being fat and anxiety as well as a decline in elevated basal beta-endorphin. These results could explain the difficulty for AN patients in gaining weight.