Wiki struggles with fatness.
Turns out that at some point it deleted its serviceable feederism page re-routing queries to fat fetishism, which is has a tangential relationship with it, if at all. If you're not sure what that is, its deviation from the required slim fetishism. That's when you find slimness physically attractive.
This is part of social politicking to tie feederism to solely to fatness in order to position 'obesity' and anorexia as opposites. Which is balderhockey because I've just realised feederism in the form of gaining, is a primary treatment for anorexia.
Not all feeders are fat nor want to get fat.
Some fill their stomachs or "bloat" with water and admire and revel in this (temporary) distention.
Basically, feederism is getting pleasure from being fed or gaining weight through eating. It can be part of sexual foreplay-incorporated into a relationship-or a thing in itself. You could just eat normally this way by for example doing without until your hunger creates an urge to binge.
This restrict/binge cycle can occur over a longer period. The urge to feederism can be related to the aftermath of long spells of high levels of physical activity-for its own sake.
There are separate parts to the phenomenon that are worth sketching out properly. Relating from memory.
Feeders; those who wish to feed someone else.
Feedees; those who wish to be fed
Gainers; those who wish to gain weight, whether they are thin slim plump or already fat.
Encourager, those wish to encourage people to be fed or to become feedees.
Fat admirer; someone who appreciates fatter bodies
Gainers associate certain higher weights with happiness and fulfilment, just like other dieters, the weight loss ones. And certain higher weights with betterment, like anorexic recovery becomes about them gaining.