Repeated consumption of a large volume of liquid and semi-solid foods increases ad libitum intake, but does not...

Food intake and a food's expected satiating effect initially rely on sensory attributes. People will learn about the food's satiating capacity by exposure. We investigated whether repeated consumption changed the expected satiety effects and intake of iso-energetic liquid and semi-solid foods. In a randomised cross-over study, participants (n=53; age: 21±2.9 y; BMI: 21.8±2.0 kg/m²) consumed one of two iso-energetic dairy foods (liquid or semi-solid) for breakfast in each 5-day test condition. Expectations regarding satiety were measured on days 1, 2, and 5. Foods were offered ad libitum on days 1 and 5 and in a fixed volume on days 2-4. Appetite sensations were rated up to 180 min after the start of the session on fixed time points. Expected satiety effects of the semi-solid food were higher than of the liquid food on all days (p<0.0001). Ad libitum intake of the liquid food was higher than of the semi-solid food on day 1 (liquid: 391±177 g, semi-solid: 277±98 g; p<0.0001) and day 5 (liquid: 477±161 g, semi-solid: 375±148 g; p<0.0001). On day 2, hunger was rated lower and fullness rated higher after the semi-solid compared with the liquid food; on day 4, no differences were observed (significant product∗ exposure interaction AUC). Changes in hunger and fullness indicated that the fixed volumes of liquid and solid food were perceived to be equally satiating after repeated consumption, but this did not result in the anticipated changes: expected satiety effects remained lower, and ad libitum intake higher for the liquid compared with the semi-solid food. The effect of texture on a food's expected satiety effects and its ad libitum intake appears to be large, also after repeated consumption. Expectations based on sensory cues are not easily changed.