I've never liked the term size acceptance. Fat acceptance is about self acceptance, if you are a fat person, because you are most definitely not supposed to accept yourself if you are a fat person.
Doing so is deemed intrinsically pathological in intent. FA tells the truth, fat people need self esteem the same as any other human.
The argument against that is that humans don't need self respect. Therefore, why should we seek to protect it in our children, and ourselves, hey, maybe we ought to actively disestablish it. Especially if it makes them better people, which it is supposed to in fat children and adults.
Because 'studies' have shown that there are racial and cultural differences in the measures of self esteem amongst especially black women, and black women are fatter some silly people have concluded that self esteem =greater levels of obesity.
Or being an uppity Negress = disease and death.
Therefore if you are a black woman you need to hate yourself more, or it'll be the death of you.
So rather than use terms such as body acceptance or size acceptance, I prefer, self-acceptance, because that's what it's all about.