Fitness (attribute)

In The Sims, a Sim's body type was fixed, and wouldn't change no matter how much he or she worked out, or ate. The Sims 2 changed that by introducing a fitness scale which appears on the Simology panel.

Sims can lose fitness by continuing to eat after their Hunger bar is full, or gain it by doing most things that increase the Body skill. If they gain or lose enough fitness, their body shape will change. Sims can increase fitness by swimming or working out on a community lot, even if they are no gaining Body skill.

Children can gain fitness by playing on swings, or jumping on the bed, though those activities don't seem to build Body skill. (This may depend on which expansion packs are installed.)