Dont you believe it. I had a daughter who was 30 pounds at 7 months and is about 200 at age 11. We were vegan vegiarians when she was little. The child eats and eats. When she was a babe I tried to cut her back to no avail. She would scream for hours our primary said give her all the food she wants, she must need it. She would drink formula until she vomited.
She has been to Boston Children's and monitered by my primary. He says there is nothing I can do. There are no fun snacks and soda at our house. He feels she is prediabatic. I think she has no off switch. I would give ten years of my life to adress this issue/
You might definitely want to look at my link on Prader-Willi Syndrome above.
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.