Do you ever make a guess to somebody who goes regularly to gym?
What is the aim or the goal?
I think you get the answer itself:
to burn fat.
to make sweat.
to get healthy.
With fit body and mind, of course you can reach almost everything you need.
More than that, now you can choose the exercise you want on gym.
Even you can join body building class to perfect your fitness :)
Somebody may has a reason to not become fat.
It makes you difficult to move, act or perform.
It looks like to lose the ideal look or self esteem when you can't control your weight, especially when your environment asked you to be slim or whatever.
But there is another reality on it.
Because for somebody else, it's ok or happy to have a fat body.
But if you now team up with others to make a campaign for a gym or health product such vitamins, nutritional food, supplements, etc, and the focus is to avoid of getting fat, you can go this copy with T-shirt:
Not fatty, but hefty