I agree with your assessment. Sometimes people are in denial because they don't want to take the necessary steps to improve. This is not healthy either. Self-acceptance should come in for the things that can not be changed or shouldn't be changed because of the risk factors. Being healthy should always be a priority. For our children we need to model that sometimes change is necessary.

"I know a young woman who's quite obese and I'll admit it's difficult for me to watch her eat double cheeseburgers with extra cheese and laugh as she refers to herself as "fat ass." That doesn't feel like self-acceptance to me, any more than scale-obsessed behavior does. She may talk the talk and tell me that she's happy the way she is, but without some measure of self-care, is her self-acceptance real?"

What do I think? Since you ask - her self-care and what she eats is none of your business - unless she explicitly asks for advice from you. If you want to be a friend, tell her it hurts to see her refer to herself in a negative way. Then listen to what she says.

And stop judging her.

I used to call myself a "fat ass". Thanks to the Fat Acceptance movement, I no longer do so. My whole life, at every weight I've been, I have exercised self-care. I'm very healthy, eat well, exercise regularly. Calling myself names was not a healthy "clue" that I should, you know, lose a few pounds (p.s. that is about SIZE) - it was a negative behavior enforced by way too much societal pressure to be thin.