Control of food intake

Over the long-term food intake and energy expenditure must be in balance if body weight is to remain steady. Eating is a goal-directed behavior controlled in the shorter term through hunger signals that motivate feeding, and satiety signals, which reduce it. An agent, neuron or pathway which stimulates appetite is said to be orexigenic, those which sup- press appetite are anorexigenic. Food intake and energy expenditure are additionally regulated by hormones released from white fat cells (adipokines). The neural networks responsible for central regulation of feeding and energy expenditure lie in the hypothalamus and in the nucleus of the solitary tract, which lies in the medulla.

However, the control of eating is a complex phenomenon that involves the reward system, affect, learning, and memory, all of which is colored by social and cultural contexts. Wealthy humans have ad libitum access to high fat, high carbohydrate foods rarely encountered in the past, eat when they are not hungry, and have far less need or opportunities for exercise. Obesity is the result for many.