The fat acceptance movement is utterly tied up in feminist bullshit, and exists because it's a taboo that affects women.Empowering fat women while fat men are completely and utterly invisible.
It would shine quite a light to this silliness if fat men mirrored the fat acceptance movement using the same platitudes and virtue signals of the female fat acceptance movement. Unfortunately they're so medicated and sedated by tech and entertainment that there's nothing to be done with this lost generation.
"Body positivity" will never apply to things that either don't apply to women (baldness, penis size) or aren't taboo for women (shortness), even if those things are actual, immutable states of being and, one would think, more worthy of "acceptance", as opposed to fatness which is easily preventable and has a thousands benefits well beyond just not being seen as an ugly failure by the opposite sex (or same sex for that matter).
Fatness is a character flaw, and feminism is all about making women's character flaws into stunning and brave statements.