How does Chris Crutcher use imagery in Staying Fat for Sarah Byrnes?

Imagery:

"We became friends when I was as fat as she is ugly, and I promised a long time ago that I would never turn away from her—told us both that my feelings for her weren't selfish, that I didn't like her only because we shared 'terminal uglies', as she put it."

"It doesn't make me proud to say this, but even with all the work I've done on the shimmering nerd I once was, there is a scared little fat boy inside me who is terrified of being seen."