The starvation mode and very overweight people (50+ lbs) really don't go hand in hand. Your body does not shut down nor does weight loss stop, just because you are in a "big" deficit relative to your maintenance level.
Your body is smart. It will only invoke the starvation response mechanism once it knows that your energy reserve (read fat) is getting low. Leaner individuals have to worry about starvation mode. Bigger people, not so much.
That said, I would never advocate 1000 calories to anyone, let alone someone who is big. It is true, the fatter you are, the more weight you can lose on a ratable basis and have that weight consisting mostly of fat, opposed to muscle.
However, eating such at extremely low amount (for the original poster, 4 calories per pound) I assume would lead to muscle loss for someone with such a high maintenance caloric level.
There are a host of other variables that come along with eating so little: Namely, is it really sustainable over the long haul? Most likely you think yes. But your body is a very adaptive mechanism. If you are not giving it what it needs, it will change you (hormonally) to increase appetite and make you eat more.
Tom was right, above. Our food selection plays a major role in how hungry we will feel. I would be willing to bet that you are eating the wrong things.
Even if you aren't, I would be willing to bet you are not getting enough of the macro and micronutrients someone of your size needs.
Maybe you could provide a sample of how you eat?