Hunger is primarily regulated by two centers in the brain: the hunger center, which stimulates eating, and the satiety center, which reduces the feeling of hunger and tells us we are "full." Whenever the level of the simple sugar glucose in the blood falls to a certain point, neurons in the hunger center are stimulated. Receptors in the stomach and a hormone released by the small intestine also send signals to the brain. Another hunger regulator monitors long-term body weight. Both the motivation to eat and overeating are influenced by biological, psychological, cultural, and environmental factors. The drive-reduction perspective says that being hungry depends on how much food we have consumed recently and how much energy is available for organ function.
Thirst parallels hunger in that both internal and external cues can trigger the thirst drive. Dehydration both inside and outside the cells prompts activation of the thirst drive, so do weather conditions as well as social, psychological, and cultural influences, and other external stimuli.
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The psychology of what we eat is determined by external factors such as the sight and smell of foods, and cultural preferences. Genetic factors also play a major role in determining who is thin and who is overweight. But, we are a nation that places a high premium on thinness. This motive to be thin has lead to an increase in eating disorders. At first, eating disorders were associated with young females, but now eating disorders affect both genders and can occur across the life span. |
Anorexia nervosa is a serious eating disorder associated with an intense fear of weight gain and a distorted body image. Another eating disorder, known as bulimia, is characterized by binges of eating followed by self-induced vomiting. Eating disorders are notoriously difficult to treat, especially in a culture obsessed with dieting. For more information on anorexia nervosa or bulimia, see the web sites for The National Association of Anorexia Nervosa and Associated Disorders and National Eating Disorders Association.
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