<qa>  What is the primary objective of the study?This study will investigate the effects of 6 week Nicotinamide Riboside supplementation 1000 mgday on metabolic health in healthy preobese humans. The primary objective will be hepatic and whole body insulin sensitivity. Secondary objectives, to provide information about the underlying mechanism, will be muscle mitochondrial function, brown fat activity, ectopic lipid accumulation, energy metabolism, cardiovascular risk parameters, body composition and acetylcarnitine levels. 