I love love love to see my sweat soaked clothes. I never really thought about it in terms of 'fat leaving', (now I will though!) but it always reminds me of junior high and high school and how all the really fit people who actually participated in all the 'fun' stuff were so athletic, and..well...sweaty. So I think it's always been a secret fantasy to be like fit and popular and fun like that - and it's represented by sweaty clothes.
That sounds just so silly and weird. But it's true.