Would it be possible to mod foods so each fulfills hunger differently? We could then feed them on salads and stuff that don't fulfill their hunger meter fully so they will stay in shape for longer. Though it is good having all foods fulfill hunger fully, it's less time consuming.
Eating a single meal past the hunger bar does not cause weight gain, so having a less satisfying food makes little sense. Sims only get fat if they eat a different plate of food while full, (or, I believe, eating a second plate of food that subsequently pushes them past full), which will also give them the "stuffed" moodlet.
If you want quick hunger satisfaction, go for a quick meal.