Glycemic and hormonal responses to two breakfast mixed meals were studied in six obese subjects with NIDDM. The study evaluated a high-glycemic-effect (HGE) and a low-glycemic-effect (LGE) meal, each with approximately 600 kcal and 12% protein, 15% fat, and 73% carbohydrate. Plasma insulin and counterregulatory hormones were measured at baseline and at 30-min intervals for 5 h after meals. Mean fasting plasma glucose and insulin concentrations were similar before both studies: for the LGE meal, 11.9 +/- 1.8 mmol/L and 261.9 +/- 50.1 pmol/L; for the HGE meal, 11.9 +/- 2.0 mmol/L and 262.6 +/- 43.1 pmol/L. Peak plasma glucose concentrations were approximately 25% lower with the LGE meal and the area under the glucose curve was 63% of that obtained for the HGE meal (p less than 0.05). Although the integrated insulin responses of the two meals did not differ, the peak occurred 60 min earlier in the LGE meal (p less than 0.05). The LGE meal may produce a lower glycemic response, in part because of earlier insulin secretion.