(A) A schematic diagram showing bilateral viral injection into the POA of Leprflox/flox mice. (B) AAV-GFP:Cre injection resulted in about 80% reduction of pSTAT3+ cell numbers in the POA (n = 6 for AAV-GFP, n = 9 for AAV-GFP:Cre; independent t-test, p<0.001). (C–E) Body weight, food intake, and energy expenditure were similar between groups throughout the study (repeated measures ANOVA followed by Bonferroni pairwise comparisons, p>0.05). (F) Energy expenditure comparison between ad lib fed (n = 10), fasted +saline (n = 5), fasted +leptin (n = 5; 5 mg/kg, i.p.), and 2-week-long HFD feeding (n = 5). Leptin injection attenuated fasting-induced hypometabolism while HFD increased the metabolic rate. Bars with different letters denote statistical significance at p<0.05 (one-way ANOVA followed by Bonferroni pairwise comparisons). (G) In LeprPOA KD mice, fasting did not decrease energy expenditure, thus leptin failed to attenuate fasting-induced hypometabolism (repeated measures ANOVA followed by Bonferroni pairwise comparisons, *p<0.05, **p<0.01).