Obviously I'm coming from a D/s context, but part of the role play could be a person's decision to make their partner fat / to be fattened by their partner and to have no hand in how much or when that decision is made.
Speaking as a Domme who made such a decision, the crucial thing is to not fatten your partner when they have expressed outright rejection of the choice. If, however, you're in a relationship and they say something along the lines of, "If you wished me [ to be fatter ] that choice is up to you" then I think they have given their consent to be fattened "with/out permission".
Unless you're getting into a relationship and they have mentioned feederism or something like it before, I would say, even as a Domme, that doing it without some kind of consent is abuse.
Whilst D/s relationships can be complicated, I think feederism can fall into a similar path. The distinction between "consent" and "abuse" can be blurry, especially to the outside.
To any feedees, I would support any kind of verbal "I give you consent to..." and for feeders I would encourage any kind of verbal "I want to..."
Sometimes these can decrease the spontaneity and fun, but it is always important that both people are ultimately happy about their relationship.
That's my cheesy take on it.
5 years