Not getting fat is the easiest thing in the world to control, I've been doing it for decades no problem. One year I purposely tried to get fat just to see how everyone else let it happen, ate whatever whenever. Gained a decent amount of weight before I was disgusted with myself and then lost it later with a sensible diet. It wasn't a big deal.
The key is disciplining yourself and not attaching too much joy to food, it has to be a kind of chore most of the time like going to the bathroom or showering or whatever. You can still eat junk food, just not constantly like many people do.
Really the whole thing is a trivial concern in this life when you factor it into the big picture, there are much worse things to be afraid of.