While I try to let their food dish go empty for a few hours in between, they typically have dry food available to them 24 hours a day. 3 of my 4 cats are of healthy weight. Dot, who had pyometria last August and thus her girly organs removed, has become a tubbo. She bats around the food dish if it is empty and sits there like a martyr. I swear these animals are smart! LOL. Despite the fact that she has a big belly, she is very active and healthy, so I'm not too worried. We rarely feed them treats or human food just to make sure they are healthy. And I feed them wet food once a week or so as treats. Obviously, they get fresh water at least once a day, but if it's extra warm or the household has been active (and thus hair has flown around), I refresh the water as needed.
The only bad side effect to having food available to them often is that the litter boxes get full QUICK! They don't eat as much as me, yet they go about 4 times more than me. Geesh!