Increasing the protein content of a beverage reduces subsequent intake at the next meal.

Abstract

Protein is widely considered to be more satiating than carbohydrate. However, it is unclear whether this rule applies equally to drinks as solid foods. Discrepancies in the literature may indicate a critical level of protein (PRO) is required in drinks, to obtain differences in appetite between CHO and PRO. In this repeated measures, cross-over design study, 28 lean male volunteers (18–35 yr) ate a standard breakfast in the laboratory and 210 min later consumed one of four preloads 30 min prior to an ad libitum pasta meal. Three of the preloads were isocaloric (∼278 kcal) mixed composition dairy fruit drinks (300 g) of low (12.5% energy PRO/87% energy CHO), medium (25% energy PRO/75% energy CHO) and high (50% energy PRO/50% energy CHO) protein content. The control drink was a low energy (78 kcal) alternative (12.3% energy PRO/84.3% energy CHO). ANOVA linear contrasts indicated a dose-response effect of preload protein level on intake (g) at the ad libitum meal ( F (1, 24) =16.15, p <0.001). Subsequent intake in each condition was: control (637.5±39.7 g), low (596.9±40.5 g), medium (546.9±34.7 g), and high protein (533.6±42.3 g). Participants did not compensate fully at lunch for the additional energy in the test drinks, however, in the high PRO condition alone, total energy intake was not significantly different from the control condition. There were no differences in ratings of hunger and fullness across conditions. Our findings support the view that increasing the protein composition of beverages could be of interest to prevent short-term positive energy balance.