When the exercise and/or overeating stops, the temporary values should slowly start reverting back to their genetic ones again on their own. When a sim does a strength/cardio workout or overeats beyond having the Stuffed moodlet, it is their temporary fitness and weight values that change. The way this works is that sims have two each values for their fitness and weight, one is genetic (more permanent) the other is temporary. The short answer is not really but there are other ways to address that.
Moving this to Chatterbox (general discussion board) since Site Help and Feedback is about this website, not the mods themselves.
