I really like Discover University's addition of bicycles as another way to exercise and keep fit! Not really a fan of its absence of any and all effects on body weight/muscles. I never like to use them since I end up with blimped-up maxed fitness level sims if biking is the only means of exercise I'm going with with their routine. Unfortunately, I only know how to change preexisting values so adding a "fitnessfat" modifier is beyond me. If anyone is able to throw a quick tweak in there it'd be greatly appreciated!
It all depends on what kind of lifestyle your Sims character has led up to this point. Active Sims will always love fitness and will do it often. If your character previously led a sedentary lifestyle, it would be better if you looked in the settings for how to activate fitness mode. It's like a person - an active person will always feel great and play sports. But for an overweight person, supplements may be required to form muscle mass, a different diet, and training. Sims are very similar to humans; take this into account.
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