(A) Adult male, wild-type mice were housed at the start of the dark cycle following body-composition measures and were maintained in temperature-controlled chambers set to either mild cold (14°C) or, as control, room temperature (22°C) for 5 days. Following a final body-composition analysis, animals were sacrificed and hypothalamic punches rapidly dissected. Mean dark and light cycle (B) core body temperature, (C) heat production, and (D) energy intake over 5 days while housed at either 22°C or 14°C. Change in (E) body weight, (F) body fat, and (G) lean body mass at study end in the same mice, n = 7–8 per group, mean ± SEM. Student’s t-test, *p<0.05 vs. 22°C. (H) Hypothalamic mRNA levels of agouti-related peptide (Agrp), neuropeptide Y (Npy), pro-opiomelanocortin (Pomc), and pro-melanin concentrating hormone (Pmch) as determined by qRT-PCR, mean ± SEM. Two-way ANOVA with Holm-Sidak correction for multiple comparisons, *p<0.05, **p<0.01, ****p<0.0001 vs. 22°C.