Genuine participation is usually diversity. If you have one master account, use it to stay active in multiple niches instead of strictly for promotion. If you used a product and lost weight, then weight loss is not all about your life. You'll have other interests like lifestyle, entertainment, sports, etc. I have seen in reddit that whenever users find someone suspicious, they check the profile and see other posts. If you only post about weight loss, then it clearly looks like a marketing account. If you only discuss about a single product or service, then it clearly reveals your strategy.