There's a lot of claims made about various foods with some saying they help 'gut health'. I would think a good mix of less processed foods could do that. People tend to want quick fixes and will do for what appear to be easy options. Marketing is a big part of that and we all love a sweet treat, me included.
My son is into his fitness and is now a physical trainer. He does some recipes on Insta, but I think they use fresh ingredients. He has encountered some people using dodgy substances at the gyms, but he doesn't do that stuff.