Because Crtc1‒/‒ males may have earned less rewards during acquisition of saccharine self-administration, an observation in line with a previous report of ours indicating that these mutant mice moved less in response to moderate stressful environments8, we considered the possibility that Crtc1‒/‒ males obesity could also depend on insufficient energy expenditure. This evidence concerns the gene CRTC1 and obesity due to melanocortin 4 receptor deficiency.