Effect of whey protein and glycomacropeptide on measures of satiety in normal-weight adult women

• Glycomacropeptide may explain how whey protein affects satiety in adult humans.
• Food intake at a subsequent test meal and rated appetite feelings were assessed.
• Satiating effect of whey protein greater than with glycomacropeptide alone.
• Satiating effect of whey protein similar regardless of glycomacropeptide content.
• Glycomacropeptide content of whey protein does not seem to play a role in satiety.

Protein is the most satiating macronutrient and dairy whey protein is thought to be more satiating than other protein sources. The purported satiating effect of whey protein may be attributable to the presence of glycomacropeptide (GMP). The objective of this study was to investigate the role of GMP in the satiating effect of whey protein. Isoenergetic (~1600 kJ) preload drinks contained GMP isolate (86% GMP, “GMP”), whey protein isolate (WPI) with 21% naturally occurring GMP, WPI with 2% naturally present GMP, or maltodextrin carbohydrate (“carbohydrate”). Satiety was assessed in 22 normal-weight adult women by determining the consumption of a test meal provided ad libitum 120 min following ingestion of a preload drink, and also by using visual analogue scales (VAS) for rating feelings of hunger, desire to eat, prospective consumption and fullness (appetite). The ad libitum test meal intake was significantly different between the preload drinks (p = 0.0003), with food intake following ingestion of both WPI preload drinks (regardless of the amount of GMP) being ~18% lower compared with the beverages enriched with carbohydrate or GMP alone. There were no significant differences (p > 0.05) in the VAS-rated feelings of appetite among the four preload drinks. GMP alone did not reduce subsequent food intake compared with a drink enriched with carbohydrate, but whey protein had a greater satiating effect than carbohydrate. The presence of GMP in whey does not appear to be the cause of the observed effect of whey protein on satiety.