CLAMS assessment of metabolism and energy expenditure in adult females demonstrates that BAT cKO mice have A, increased mean oxygen consumption (VO2) during the dark phase (light phase showed non-significant trend to also be elevated), and increased mean B, carbon dioxide production (VCO2), and C, energy expenditure (heat divided by kg lean mass) during both the dark and light phases. D, Mean RER did not differ between genotypes, whereas E, mean activity levels were significantly elevated in BAT cKOs during the dark phase. n = 14–15/group. *P < .05; **P < .01, #P = .06