I can try to answer this. Though I don't recall ever asking directly, exercising is of interest to me. Firstly, it is a common interest. I want a partner who enjoys hiking. For someone else that may be biking or swimming. Secondly, a partner who works at looking good is attractive. Most women pay lots of attention to hair, makeup, clothes, shoes :-) To me, it is even more attractive if a woman looks good wearing plain clothes with little or no makeup. Finally, there are emotional and psychological advantages to exercising. It is a good way to clear your head. Jogging is a good time for self reflection and prayer. And pushing your self and showing commitment are attractive traits.
I hope that helps though I can not speak for every guy.
But why put anything about beauty in the first place?