Cerulenin, a natural fatty acid synthase (FAS) inhibitor, and its synthetic analog C75 are hypothesized to alter the metabolism of neurons in the hypothalamus that regulate ingestive behavior to cause a profound decrease of food intake and an increase of metabolic rate leading to body weight loss. The bulk of data exclusively originates from mammals (rodents), however such effects are currently lacking in non-mammalian species. We have, therefore, addressed this issue in broiler chickens, because this species is selected for high growth rate and high food intake and is prone to obesity. We have firstly demonstrated that FAS messenger and protein are expressed in the hypothalamus of chickens. FAS immunoreactivity was detected in a number of brain regions including the nucleus paraventricularis magnocellularis (PVN) and the nucleus infundibuli hypothalami (IN), the avian equivalent of the mammalian arcuate nucleus suggesting that FAS may be involved in the regulation of food intake. Secondly, we have shown that hypothalamic FAS gene expression was significantly (p<0.05) decreased by overnight fasting similar to that in liver indicating that hypothalamic FAS gene is regulated by energy status in chickens. Finally, to investigate the physiological consequences of in vivo inhibition of fatty acid synthesis on food intake, we administered cerulenin by IV injections (15 mg/kg) to 2-wk-old broiler chickens. Cerulenin administration significantly reduced food intake by 23 to 34% (p<0.05 to p<0.0001), and down regulated FAS and melanocortin receptors (MCR-1, -4 and -5) gene expression (p<0.05). However, the known orexigenic (NPY, AgRP, ORX and ORXR) and anorexigenic (POMC and CRH) neuropeptide mRNA levels remained unchanged after cerulenin treatment. These results suggest that the catabolic effect of cerulenin in chickens may be mediated through the melanocortin system rather than the other neuropeptides known to be involved in food intake regulation.