Background: Whey protein is more satiating than other protein types, including casein. We hypothesized that enhanced satiety with whey protein is related to glycomacropeptide (GMP) content, a stimulator of cholecystokinin (CCK).
Objectives: To investigate the role of GMP in whey protein-induced satiety, as measured by subjective satiety, CCK release and food intake at a test meal in healthy weight men and women.
Design: In a within-subjects design, twenty subjects (n=10 men, 10 women) consumed 1 of 4 preload shakes (300 mL, 1 MJ), 1 week apart. Preloads differed by protein source and content: Whey; whey protein isolate, Whey (-)GMP; whey protein without GMP, Control; low protein, GMP; GMP isolate. Protein energy of preloads was 44, 44, 2 and 3%, respectively. Subjective satiety and CCK were measured at 0, 15, 30, 45, 60, 75 and 105 min post-preload consumption. A lunch test meal was provided at 75 min. Food records were completed weekly.
Results: Pre-meal satiety was greater after whey protein preloads compared to Control and GMP preloads in women, but no difference was evident in men (sex by preload, p<0.03). CCK concentrations followed a pattern that predicted the subjective satiety in women, but not in men. Test meal intake was not different by preload; however, compensation relative to usual daily intake was achieved after whey-containing- and GMP-containing preloads in women and after GMP and Control preloads in men.
Conclusions: GMP alone is not critical in pre-meal whey-induced satiety; however, it may have a unique role in compensatory intake regulation managing daily energy intake.