The aim of the present study was to investigate the effect of a monosaccharide/fiber preload (galactose/guar gum) in combination with a standard breakfast (GG) on plasma GLP-1, insulin, glucose, free fatty acid concentrations, and appetite ratings (satiety, hunger, fullness and desire to eat) in 30 normal-weight subjects. GG was compared to water in combination with the standard breakfast (W). We also tested for differences in GLP-1 release in the described conditions between genders. In women, postprandial plasma GLP-1 concentrations after GG were significantly increased compared to W (p < 0.05). The area under the curve (AUC) for DeltaGLP-1 after GG was related to body fat (%BF) in women (r = 0.48; p = 0.02), but not in men. The rise in plasma insulin was delayed, and plasma glucose concentration was blunted after GG. Deltasatiety was significantly related to DeltaGLP-1 (W). In conclusion, galactose with guar gum increased and extended the GLP-1 release due to breakfast in women, but not in men. This may be partly explained by %BF, which is higher in women than in men since GLP-1 release appears to be related to %BF.