Niche-specific social media app (fitness-only)

Hi all , I have a startup idea, I don't know if it's already implemented by anyone. Niche based social media app Whenever we use social media we will get hooked to one particular niche like food and the niche will eventually change to fitness or sports or entertainment. I'm thinking of creating an app which will focus on only a few particular niches. For example only fitness related app where influencers and content creators and people who want to see or love to see only content related to fitness and nothing else. I believe it won't be a distraction because no other content will appear on it except fitness.