Economics of Obesity

Whenever I hear about someone who weighs 500 or 600 pounds or more, I always want to hear about their livelihood.

What do they live on?
What is their source of income?
Who supports them?
It must cost a lot to feed someone who is that fat.
They also seem to have special needs, expensive special needs..

So who pays for it?
That should always be part of the story.
Who pays to keep the person fat.
Who buys the food

what is the economics of obesity?