Sims gaining weight

I'm not so happy that this happens to all the sims you play cause you get them to eat when they are hungry. One thing I do the slow down the weight gain is monitor how fast the food intake is and stop them eating when they are full or use U.I. Cheats and make their fullness go down so they can eat the entire amount of the meal. Exercise does help to keep the weight off but they do gain weight if you play on particular Sim a bunch. So then I use Cas.fulleditmode shift click the Sim in question and go into CAS and make them to the original proportions I gave them. I love The Sims but this is a little irritating that they gain weight so easily. Oh pool at home and swimming laps everyday helps too.