Regulation of food intake and body weight depends on direct and feedback signals from adipose tissue, alimentary canal and pancreas to the hypothalamus nuclei, where hunger and satiety centers are. During the last decade a few signaling molecules of peptide origin were discovered, which play an important role in the regulation of energy intake and energy expenditure as well as in obesity. So, adipocytes synthesize and express leptin, the product of Ob gene, a regulator of long-term food intake, in amounts proportional to the fat amount, while alimentary canal hormones are regulators of short-term food intake (from meal to meal). Some peptides decrease food intake as they promote satiety (anorexigenic signals), other peptides, contrary, increase food intake as they induce appetite (orexigenic signals). Disturbed equilibrium between the anorexigenic and orexigenic factors manifests as food intake disorders, increase in body weight and obesity or decrease in body weight, i.e. cachexia.