Effect of Dietary Glycemic Index on Beta-cell Function

Following a 2 week medium glycemic index control diet (glycemic index 50-55), subjects will be provided with a weight stable low glycemic index diet (glycemic index \<35) for 4 weeks with all food provided by the Human Nutrition Lab

Following a 2 week medium glycemic index control diet (glycemic index 50-55), subjects will be provided with a weight stable high glycemic index diet (glycemic index \>70) for 4 weeks, all food provided by the Human Nutrition Lab. They will take placebo capsules (matching for active N-acetylcysteine (NAC) in arm 3) twice daily for the 4 weeks on the high GI diet. The NAC vs. placebo arms (arms 2 and 3) will be double-blinded.

Following a 2 week medium glycemic index control diet (glycemic index 50-55), subjects will be provided with a weight stable high glycemic index diet (glycemic index \>70) for 4 weeks, all food provided by the Human Nutrition Lab. They will take N-acetylcysteine (NAC) two 600 mg capsules twice daily for the 4 weeks on the high GI diet. The NAC vs. placebo arms (arms 2 and 3) will be double-blinded.