Using a within-subjects design, we gave over-weight and normal-weight subjects a 500-mL drink of fructose, glucose, or aspartame diluted in lemon-flavored water or plain water in a randomized fashion at about weekly intervals. Food intake was assessed at a buffet lunch that began 38 min after the preload was completed. Blood was drawn throughout and assayed for concentrations of glucose, insulin, glucagon, and free fatty acid. When subjects drank the fructose preload, they subsequently ate fewer overall calories and fewer grams of fat than when they drank any of the other preloads. The aspartame load did not stimulate intake beyond the plain-water control. The effects of the oxidation of fructose as a possible mechanism for the reduction in food intake is discussed. The effects of insulin in stimulating intake are also discussed.