I have this issue, just not related to eating disorders. It's such a small, intimate space with nothing else for my T to focus on, and I despise being the center of attention. I am painfully aware of every single flaw of mine during those 50 minutes, and it changes what I say and how I say it. I can be direct about anything in writing, but she has me read any writings aloud, so I just don't bring any.
The only time I felt more at ease was when I decided to lie down. My position made it more awkward to look at her than not, so her staring, facial expressions, and body language weren't my focus.