I can imagine that it's good for their ego. ''I need to wear a fat suit to understand really obese people, and oh wow, the suit does not look like me, but way fatter! And when we discuss out experiences, I'll be one of the ''healthy'' people discussing what it's like to be so FAT.'' That, coupled with the ''understanding'' attitude/approach they're promoting towards being so massively fat, sounds like heaven for these fatties.