I would think, with all the attention and care he's getting, they would have diagnosed him with a medical issue causing the weight, and he would be also receiving treatment for it. "It my thyroid" or "It's hormonal" are common rationalizations, and almost always undiagnosed by a doctor.
You CAN eat yourself to this size. I've seen a lot of the shows about people this big on the science channels, and none of them had hormonal or medical conditions that caused the weight - in most cases it was depression, lack of activity, binge eating, and emotional issues. Once you hit the point where you cannot get out of bed, sit up, or anything else, it's a fast road to 1000 pounds or more, most of it fluids and such that build up in the body. Almost all of them, once they're in a controlled environment where they cannot get food, or have it brought to them, and they eat rationally and healthy, and are in a therepuetic environment with encouragement and positive attitudes, they lose weight.
Granted, at 1200 pounds his blood chemistry and body are a complete train wreck, but in a controlled environment and a stable diet, it should come back to normalcy eventually - and the weight will come off.
"but in a controlled environment and a stable diet, it should come back to normalcy eventually - and the weight will come off." -If he survives till then.
Atkins diet.