Does Inositol Make You Gain Weight?
There is no strong evidence that inositol directly causes weight gain in most people. In fact, some research looks at inositol in the context of insulin resistance, metabolic health, and even body mass index. That does not make it a weight-loss supplement, but it does mean weight gain is not a standard expected effect in the research. (PMC)
So why do some people think it causes weight gain? The most likely reason is that some users experience bloating, stomach discomfort, or digestive changes when they start taking it. That can make the body feel heavier or puffier, even if actual fat gain is not happening. Mild gastrointestinal side effects are well known with inositol, especially at higher doses. (WebMD)
Weight changes are also hard to judge in people with PCOS or insulin resistance because their body weight may already be shifting due to hormones, appetite, water retention, diet changes, menstrual cycle patterns, or other medications. It is easy to blame one supplement for a change that actually has several causes. Research does not support the claim that inositol normally causes true weight gain as a direct effect. (PMC)
The short answer is this: inositol is not known as a typical cause of weight gain. If someone feels heavier after starting it, bloating or digestive side effects may be the more likely explanation than actual fat gain. (PMC)