Time course of effects of preloads high in fat or carbohydrate on food intake and hunger ratings in humans.

A high-carbohydrate (CHO) yogurt (81% CHO) and a high-fat yogurt (65% fat), containing similar levels of protein, were given in equal volumes as preloads to 14 normal-weight, nondieting males and 14 normal-weight, nondieting females. The yogurts were formulated to have similar energy densities and sensory properties, so that differences in responses to the preloads would depend on postingestive physiological effects. Three intervals (30, 90, and 180 min) between the preloads and a self-selection meal consisting of a variety of foods were utilized. The self-selection meal was served at the subject's normal lunchtime under all conditions. In the 30-min-delay condition, subjects accurately compensated for the calories in the preloads compared with a no-preload condition, but as the interval increased, compensation was less precise. No significant differences in subsequent food intake were found between the high-CHO and high-fat yogurts at any time interval. Also, there were no differences in ratings of hunger and fullness between the yogurts. The macronutrient composition of the preloads did not affect the types of foods, or macronutrients, consumed at lunch.