Does NAD+ cause weight gain?

Human studies on NAD+ supplements such as NMN and NR do not report weight gain as a side effect. However, it is worth noting that those studies were not designed to measure it, and the participant groups were small. There is simply no indication that NAD+ supplements cause you to gain weight.

Animal research actually points in the opposite direction. In mouse studies, NR supplementation protected against weight gain induced by a high-fat diet. This worked through enzymes that improve energy metabolism in the energy-producing compartments of cells. Other mouse studies showed that higher energy expenditure led to lower fat mass and protection against obesity. However, results in mice do not automatically translate to humans.

In humans, one randomised double-blind study lasting 10 weeks was conducted in postmenopausal women with prediabetes and excess weight. NMN improved insulin sensitivity in muscles, but weight was not a primary outcome. In a completely different context, in cancer patients experiencing muscle and weight loss, NAD+ supplementation through niacin (vitamin B3) actually helped limit that loss. This says nothing about weight gain in healthy individuals.

In short, there is no evidence that NAD+ supplements cause you to gain weight. The research is limited in scale and rarely measures weight as an outcome. It is too early to make a definitive statement in either direction.