A study was conducted to determine the effects of various levels of gastric distension on spontaneous meal intake. A balloon was inserted into the stomach of four lean and four obese subjects before consumption of a lunch meal. On different days the balloon was filled with 0, 200, 400, 600, and 800 mL water in a random sequence. As balloon volume increased, food intake decreased, with a balloon volume of greater than or equal to 400 mL significantly reducing intake (p less than 0.01). There was no significant difference between lean and obese subjects. Because gastric emptying rate was not significantly slowed by a volume of 800 mL, between emptying was probably not a factor in inducing satiety. Discomfort was probably also not a factor because it was experienced by only two lean subjects at 800 mL. Most likely gastric distension itself triggered satiety signals.