The primary findings of the present study using small (10 g) to standard (75 g) glucose loads are: i) insulin resistance and hyperinsulinemia; ii) decreased insulin disposal (P < 0.001); iii) trend for reduced GLP-1 responses at 75 g glucose and unchanged GIP responses; and iv) increased fasting glucagon levels in obese, non-diabetic subjects compared to lean controls. The gene discussed is GCG; the disease is hyperinsulinism.