Background: Proteins are more satiating than fat and carbohydrate but in a sourcedependent
manner. Whey Protein Isolate (WPI) and Glycomacropeptide (GMP) suppress
Food Intake (FI) in both humans and animals. The objective of this study was to compare the
effect of whey protein and GMP preloads on regulation of FI and blood glucose in male
Wistar rats. In this study, Rats were allocated to five groups and received one of following in
a cross-over design: 1) water; 2) WPI; 3) WPI+devazepide (CCK-1 receptor blocker);
4) GMP; and 5) GMP+devazepide. Food intake, plasma glucose, insulin, CCK and ghrelin
Results: Plasma CCK concentration was higher 30 min after administration of WPI and GMP
compared with the water control. Devazepide increased FI when it was co-administered with
WPI and GMP preloads at 1 hour compared with FI after administration of WPI or
GMP alone. Ghrelin was lower after WPI administration compared with water control. No
differences in glucose and insulin concentrations were observed.
Conclusion: CCK-1 receptors mediate FI suppression induced by both WPI and GMP.
However, this effect is limited to the first hour of FI. No differences in the effect of WPI and
GMP on glucose metabolism were observed.