Food intake and the regulation of body weight

This chapter reviews the recent literature on hormonal and neural signals c ritical to the regulation of individual meals and body fat. Rather than eat ing in response to acute energy deficits, animals eat when environmental co nditions (social and learned factors, food availability, opportunity, etc.) are optimal. Hence, eating patterns are idiosyncratic. Energy homeostasis, the long-term matching of food intake to energy expenditure, is accomplish ed via controls over the size of meals. Individuals who have not eaten suff icient food to maintain their normal weight have lower levels of adiposity signals (leptin and insulin) in the blood and brain, and one consequence is that meal-generated signals (such as CCK) are less efficacious at reducing meal size. The converse is true if individuals are above their normal weig ht, when they tend to eat smaller meals. The final section reviews how thes e signals are received and integrated by the CNS, as well as the neural cir cuits and transmitters involved.