What can you talk about in "Additional Information"?

At the very end of the common application?

“Please provide an answer below if you wish to provide details of circumstances or qualifications not reflected in the application”

I had been huge (in a bad way) throughout my teens and early 20s, but lost over 100lbs and am now an avid gym rat, is that something that I could talk about there?

Eh not really. That could have been something you mentioned in your essay. That portion is more or less for describing “life situations.”