The length of time you could survive without food depends on so many variables that its just impossible to say. But I'm going to go out on a limb and say that someone weighing in at 1100 lbs isn't in very good health and therefore wouldn't last long. Having all that extra fat wouldn't translate into longer survival, if that's what you were wondering.
Hard to say, but they'd probably die well before anywhere near any large weight loss. The body might go into shock, shut down & boom. Just like when people have starved for a period of time, they begin to eat a lot & bang. We really discovered the dangers & had the ability to figure it out during WW II when the first concentration & death camps were discovered. The normal reaction is to eat, the normal behavior was to give these folks food, it was picked up after comparing notes-they were eating themselves to death, just to much stress on the body. If you want to know in fairy tale land 3500 cals is a pound, dump a 1000 lbs, simple math
Your body needs about 1,200 calories a day to function & survive - support breathing, brain function, organs, maintain general health. (About 2,000 calories if you're a guy.) Both men & women must burn 3,500 calories to lose just one pound of fat. You'll have do the math.