Have you tried the weight loss icecream? Sims are dropping weight like mad and get a happy mood buff from it. I completely forgot about this, easy mode for my lazy sims who don't want to work out.
I love that ice cream. Sims can enjoy all the sweets they want and then one weight loss ice cream later they're back to the start. I use it when I want my sim to lose weight but don't want them to become athletic and muscular. I had a female sim who looked horrible after her athletic skill was maxed trying to lose weight. Muscle didn't look good for her.