Changes in body weight (A), fat mass (B), fat free mass (C), and food intake (D) determined before and after cold adaptation protocol in Lep-/-, Lep+/- and wild-type Lep+/+ mice. The rate of an increase in food intake per degree Celsius reduction in ambient temperature in mutant Lep-/- and control mice (E). Comparison of energy utilization from endogenous reserves and food intake in mutant Lep-/- and Lep+/? controls (F). Correlations between daily increase in food consumed and internal body reserves mobilized per day in the cold (G). Data are expressed as mean ± SEM. *, significant differences between mice (t test, *, P < 0.05; **, P < 0.01; ***, P < 0.005; ****, P < 0.001). FI, food intake; FM, fat mass; FFM, fat free mass.