Giving male mice a supplement called NMN every day for a year helped them gain less weight as they aged — the higher the dose, the less weight they gained — and didn’t seem to cause any harm.

What we've found so far suggests that long-term NMN supplementation may reduce age-related weight gain in male C57BL/6N mice. The evidence we've reviewed leans toward this effect, with no studies in our analysis showing the opposite. We analyzed one assertion from the available research, which reports that giving male C57BL/6N mice NMN daily for a year was linked to less weight gain as they aged [1]. The data showed a dose-dependent response — the higher the dose of NMN, the less weight the mice gained over time. Importantly, this long-term use did not appear to cause any observable harm to the animals [1]. Our current analysis is based on limited evidence — only one assertion from the broader research pool. While all of the evidence we’ve reviewed so far supports the idea that NMN may help reduce age-related weight gain in this specific mouse strain, we don’t yet have enough data to know how strong or consistent this effect is across different conditions or studies. We also don’t know whether these findings would apply to other animals or humans, or if there are long-term risks we haven’t detected. Since we’re only looking at male C57BL/6N mice, the results may not extend to females or other genetic backgrounds. Because our analysis is ongoing, our understanding could change as more evidence becomes available. For now, what we can say is that in this one case, NMN was associated with reduced weight gain during aging, and higher doses were linked to a stronger effect. Practical takeaway: In male C57BL/6N mice, daily NMN over a year may help slow age-related weight gain — but we’re still early in the process of understanding how and why.