Leptin signaling in the brain regulates energy intake and expenditure. To test the degree of functional neuronal leptin signaling required for the maintenance of body composition, fertility and cold tolerance, transgenic mice expressing CRE in neurons (CaMKII-CRE) were crossed to mice carrying a floxed leptin receptor (Lepr) allele to generate mice with neuron-specific deletion of Lepr in ~50% (C F/F mice) and ~75% (C 17/F mice) of hypothalamic neurons. LEPR-deficient mice (17/17) with Heat-shock-CRE-mediated global Lepr deletion served as obese controls. At 16 weeks, male C F/F, C 17/F and 17/17 mice were 13.2% (p < 0.05), 45.0% and 55.9% (p < 0.001) heavier, respectively, than lean controls, while females showed 31.6%, 68.8% and 160.7% increases in body mass (p < 0.001). Significant increases in total fat mass (C F/F: p < 0.01; C 17/F and 17/17: p < 0.001 vs sex-matched, lean controls), and serum leptin concentrations (p < 0.001 vs controls) were present in proportion to Lepr deletion. Male C 17/F mice had significant elevations in basal serum insulin concentrations (p < 0.001 vs controls) and were glucose intolerant, as measured by glucose tolerance test (AUC p < 0.01 vs controls). In contrast with previous observations in mice null for LEPR signaling, C F/F and C 17/F mice were fertile and cold tolerant. These findings support the hypothesis that body weight, adiposity, serum leptin concentrations and glucose intolerance are proportional to hypothalamic LEPR deficiency. However, fertility and cold tolerance remain intact unless hypothalamic LEPR deficiency is complete.