If I were you, I would say there is something you can do. Get yourself another doctor! There most definitely is something wrong with a 200lb. 11 year old who can't stop eating. What kind of doctor says there is "nothing" you can do about something like this? If it isn't something medical or physical (as in Prader-Willi Syndrome) then the problem is psychological, in which case some major behavior modification (in a controlled environment) can be done, if you're willing. I'm sure it would be extremely tough on your whole family (and probably expensive), but I think it's worth a try. Your daughter's life depends on it.
I simply don't believe that there is "nothing" that can be done for your daughter.
In this day of managed care and evidence-based treatment, there is no treatment modalities available for her. None of her lab values are out of wack. Her cortosol values have leveled off. There just isnt anything that I can do, we have been to dieticians, and eating disordered programs, where I am told that she is just obese.
I have thought of a surgeon, but it seems extreme for eleven, even though she has stretch marks on her arms and shoulders from rapid weight gain.