Satiating effects of protein but not carbohydrate consumed in a between-meal beverage context

Previous research has suggested that protein is the most satiating macronutrient; however some experiments have found no difference in satiating efficiency of protein and carbohydrate during short intervals after consumption. There is also evidence that the satiating effects of carbohydrate are minimal when in a beverage rather than solid context. To evaluate whether protein-based satiety was evident in a drink context, and clarify further effects of preload time on satiety, the present study compared iso-energetic dairy fruit drink preloads ( approximately 1250 kJ), differing in macronutrient composition and consumed at two time intervals in the morning. Using a counterbalanced within-subjects design, 18 unrestrained lean male volunteers consumed 300 ml of carbohydrate-enriched (CHO), protein-enriched and low-energy control (327 kJ) dairy fruit drinks, 120 min and 30 min before an ad libitum lunch. Significantly less energy was consumed at lunch after the protein (3234 kJ) compared to the control (3468 kJ, p<0.05) and CHO preloads (3588 kJ, p<0.05). However, this was not sufficient to show complete energy compensation. Preload time of consumption did not impact upon any measures. Only satiety ratings at the beginning of lunch varied significantly by preload type, reflecting differences in test meal intake. These findings are consistent with previous research that protein is more satiating than carbohydrate. The roles of sensory and hedonic characteristics are discussed.