They have filters that crawl for keywords or phrases that usually indicate someone there just for a fetish fling.
First, you can only like a few people a day, unless you invite friends to join the app, an obvious attempt at getting more users.
Second, if you don't interact with the user within 48 hours of you both mutually liking each other, the "like" disappears and you lose your opportunity to talk to them, a feature that prevents endless "likes" with no contact.
But while that's true, all of the fat women in my life have at least one story of men explaining to them that they could never date because of her fatness.
It's never easy to be rejected for any reason, but fat women get used to it in their interactions with men sadly because it seems to be more socially acceptable to express disgust with fat than it is express other complaints about a person's physical appearance.
But like most humans, us fat people want people to love us for who we are, not for our bodies, or not because of our bodies.