...The aim of this study was to test the safety of dietary NR supplementation over a 12-wk period and potential to improve insulin sensitivity and other metabolic parameters in obese, insulin-resistant men...Insulin sensitivity, endogenous glucose production, and glucose disposal and oxidation were not improved by NR supplementation. Similarly, NR supplementation had no effect on resting energy expenditure, lipolysis, oxidation of lipids, or body composition. No serious adverse events due to NR supplementation were observed and safety blood tests were normal. 12 wk of NR supplementation in doses of 2000 mg/d appears safe, but does not improve insulin sensitivity and whole-body glucose metabolism in obese, insulin-resistant men.