>but do exercises to keep stomach flat
What fucking magic exercises are these that remove fat from one part of the body and put it somewhere else? It's complete fiction. Work out your stomach but eat to get fat, and you'll end up like a power lifter. Stomach hard enough to deflect gunfire, but buried under a pad of fat anyway.
Literally the only way to get rid of stomach fat, and nothing else, is liposuction. As a man, your body will prioritize keeping fat at the core, and siphon it from everywhere else, first. You can lose weight until you look like an Auschwitz survivor, and the last thing to go will be the belly fat.