Different thermic effects of leptin in adolescent females with varying body fat content

SummaryBackground & aimsInvestigating the effect of leptin on energy expenditure in undernutrition might lead to a better understanding of the role of leptin in regulating body weight in humans.Methods73 underweight female adolescents with anorexia nervosa (AN) were compared with 23 healthy normal weight (nwC), and 9 overweight girls (OW); 37 AN were followed during 7 months of weight recovery. Resting energy expenditure (REE, by indirect calorimetry), body composition (fat mass, FM; lean tissue mass, LTM; by Dual-Energy X-Ray Absorptiometry) and plasma hormones of leptin and 3,5,3′-Triiodothyronine (T3) were measured.ResultsIn underweight, leptin, T3 and REE adjusted for lean tissue mass (REELTM) were decreased; in OW, FM and leptin were increased at unchanged T3 and REELTM. There was a significant positive relation between FM and leptin at low and normal (AN, r2 = 0.26; nwC, r2 = 0.51, p < 0.001), but not at high adiposity. Leptin and REELTM were positively associated in underweight (r2 = 0.14, p = 0.001) but not in normal or overweight subjects. T3 was linearly related to REELTM over the whole range of adiposity (r2 = 0.42, p < 0.001). With weight gain in AN (5.0 ± 3.5 kg) the relationship between leptin and REELTM changed toward the conditions seen in normal weight controls.ConclusionsAt low adiposity the interrelated fall of leptin and REE reflect an adaptive mechanism to preserve body weight. High leptin production associated with excessive adiposity was without effect on metabolic adaptation.