There are umpteen billion calorie trackers, including one super popular one with a free mode that is annoying, but tolerable. I don't mean to be an asshole, but ... why would anyone pick your's?

I think at the least you should consider giving your first 10k users free passes (and yelling it at the top of your lungs, because what you desperately need are your "early adopters") ...

... or you'll never make it to 100k+ users (with some % of 90k of them actually paying you money).