Does NAD+ cause weight gain?

Human studies on NAD+-boosting supplements such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) do not report weight gain as a side effect. This is, however, an indirect conclusion: those studies were not designed to measure changes in body weight, and the participant groups were small. Based on the available evidence, there is simply no indication that NAD+ supplements lead to weight gain in humans.

Animal research points in the opposite direction. In mouse studies, NR supplementation actually protected against weight gain induced by a high-fat diet, through activation of enzymes (SIRT1 and SIRT3) that improve energy metabolism in mitochondria. Separate mouse studies showed that increased activity of Sirt3, an NAD-dependent enzyme in mitochondria, led to reduced fat mass and protection against obesity, presumably because energy expenditure increased. These are animal studies, and results in mice do not automatically translate to humans.

In humans, one randomised double-blind study of 10 weeks was conducted in postmenopausal women with prediabetes and overweight: NMN supplementation improved insulin sensitivity in muscles, but weight change was not a primary endpoint. In an entirely different context, namely in cancer patients experiencing muscle and weight loss, NAD+ repletion via niacin (vitamin B3) actually helped to limit that loss. This too has no direct relevance to weight gain in otherwise healthy individuals.

In short, the idea that NAD+ supplements cause weight gain finds no support in the available studies. The available research is limited in scale and has rarely measured weight change as a primary outcome, making a definitive statement in either direction premature. Anyone concerned about body weight when using NR or NMN is best advised to discuss this with a doctor, but there is currently no reason to assume, on the basis of scientific evidence, that these supplements cause weight gain.