Eating behavior is controlled by many factors, including appetite; food availability; family, peer, and cultural practices; and attempts at voluntary control. Eating disorders are characterized by a voluntary control of eating behavior, causing serious disturbances in normal eating habits. People with eating disorders demonstrate an extreme and unhealthy reduction or increase in food intake, as well as feelings of distress or extreme concern about body shape or weight. The three most common types of eating disorders are anorexia nervosa, bulimia nervosa, and binge eating disorder. People with anorexia nervosa have an intense fear of gaining weight or becoming fat. They are usually underweight, and resist maintaining a body weight at or above the minimum normal weight for their age and height. People with bulimia nervosa are less frequently underweight. Their eating habits are characterized by episodes of bingeing, followed by episodes of purging. Similarly, people with binge eating disorder have eating habits characterized by episodes of binge eating, but no purging. Studies on the basic biology of appetite control and the effects of overeating and starvation have revealed extensive information about eating disorders, but there are still questions to be answered. This study will use a sipping and spitting exercise to better understand the brain's response to food intake in people with eating disorders.

Participants in this observational study will first report to the Biological Studies Unit (BSU) for a screening visit. Participants will be provided with a series of sweetened beverages to taste and spit out. The beverages will be made with water, Kool-Aid mix, and sugar or artificial sweetener. Participants will rate the sweetness of each beverage and how much they like it. They will then practice sipping the beverage through a straw and spitting it out without swallowing. Those participants who feel comfortable with the sipping and spitting exercise will report to the BSU for 10 sipping and spitting exercises. The exercises may be scheduled on up to 4 separate days, and may last up to 2 hours per day. Participants will eat a standardized breakfast on the morning of the study, and then will not eat again until they report to the BSU 4 hours later. Participants will sit alone in a room alone, and sip and spit beverages for up to 5 minutes at a time. Between sipping and spitting sessions, participants will complete surveys about hunger and other sensations. They will also rinse their mouths out with baking soda and water to clear the taste of the previous beverage and to prevent discoloration of the mouth from the Kool-Aid. Measurements will include the amount of beverage sipped at a time, and how quickly each was sipped.