The present study strongly suggests that daily i.p. injections of orexin-A at 1 μmol/kg, the most efficient concentration to reduce tumor growth in mice [20], despite the fact that it modulated the expression of few brain neuropeptide receptors in the hypothalamus, did not induce major effects on the various components of energy expenditure and on long-term body weight evolution. The gene discussed is HCRT; the disease is neoplasm.