Anybody are using health and fitness for your niche blog and having success with them. I am starting to think it is too hard and saturated to work commercially on this niche.
I am not particularly sure what you are selling related to health and fitness. Is it a service to get fit? or health supplements?
Even with presence of stiff competition, you can find your niche in the market by finding your "unique selling proposition." That is a marketing term which will let your customers know why I should try your product or service.
I have seen a lot of content made specifically on health and fitness. High performing blogs talk about "dangers" on not taking care of your health which actually instill "fear" and being "conscious" of staying fit and healthy which are good signals for selling your services or products. I find testimonials especially via video marketing extremely effective. Free trial or money guarantees encourage trial offer including promo offer by way of discounts for a limited time period.
You can always check what competition is doing and look for opportunities not being served and perhaps start from there. If you believe in what you are offering and its effectiveness, then there is no reason that you should not let the market know about this. Know your target market, prepare your marketing plan, concentrate your strategies towards maximizing your introduction via platforms that can yield you the highest exposure considering your budget and time constraints.