Group A with standard carbohydrate-rich laboratory diet (chow), group B with chow + stevioside (0.03 g/kg BW/day), group C with 80% SPI + 20% chow and group D with 80% SPI + 20% chow + stevioside (0.03 g/kg BW/day), on first-phase insulin (A) and glucagon (B) during IAGTT. Values are shown as mean ± SEM, n = 12 in each group. * p < 0.01, ** p < 0.05, *** p < 0.001.