I am all about vanity, never about health. I have been blessed with a very healthy body, but I know it can only take so much abuse. I see how my Mom's health is and I would like to avoid those problems.
My career is a big factor, I am in the Military. It sucks to feel like I am not worthy to have my job of 19 years because I am so fat. Also, there are sooo many young fit people around me all the time, it amplifies to me that I am not one of them. Then there's the whole fitness testing and job requirement issues that I have to survive and I am tired of barely making it.
Being uncomfortable in bed and getting sore feet from standing or walking is a factor too.