Also, to answer to ceeceeroni...
I am assuming you are simply trying to answer the question "What are your research interests?" Hopefully, you at least made some mention of this in your person statement- make sure you match what you said in that. But, it's okay to not have your specific topic picked out for your dissertation- but don't be too broad as to say "Oh, you know, anything involving eating disorders." Give examples of things you've studied or worked with in the past and what interested you about it. I think it's also fair to say that you are excited to look into new ideas, and you just feel that this particular lab would allow you that freedom (if that's true, of course). Be sure to match it to your POI (not exactly, or they'll know you're lying/exaggerating).