The effects of d-amphetamine on food intake of humans living in a residential laboratory

Two groups, each consisting of three normal weight, male research volunteers, lived continuously in a residential laboratory for 15 days. All contact with the experimenters was through a networked computer system and subjects' behaviors, including food intake, were continuously recorded. During the first part of the day, subjects remained in their private rooms doing work activities. During the remainder of the day, they had the option to socialize with each other. A wide variety of food items were continuously available. Subjects controlled their own patterns of food intake, and could consume any item, or number of items, at any time during the day. Beverages containing d-amphetamine (10 mg per 70 kg) or placebo were consumed daily at 0930 and 1630 hrs. Amphetamine significantly reduced total daily caloric intake to about 70% of placebo levels. The reduction in intake was a consequence of a decrease in number of eating occasions per day; no changes in mean intake per occasion were observed. Amphetamine produced similar decreases in the daily number of snack and meal items, and in protein, fat, and carbohydrate intake. These results demonstrate that amphetamine has significant effects on human food intake, and the study of human feeding behavior under similar naturalistic conditions should provide important information about the behavioral actions of drugs affecting food intake.