The body positive movement doesn't glorify fatness or obesity its just saying regardless of what your body looks like, you are worthy of love and acceptance and clothes that fit and make you feel good about yourself and job opportunities etc. Being fat is not the most important thing about a person and you deserve to not hate yourself for not looking a certain way.
It's a nice movement, it goes against the standard that specifies one type of body as being good and the rest being bad, and if a person has a 'bad' body they are also more likely to have other 'bad' traits, e.g. ugly, unintelligent, smelly, lazy etc. As a movement it just promotes that people of all body types are worthy of love and respect and care.
And its annoying when people have to jump in with wanting to talk over that conversation with how unhealthy being overweight is because they can't accept that you can still be worthy of love and respect even if you are unhealthy.
Like nobody is going around saying other people should strive to become obese, or that obesity is always healthy and an ideal, but the reality is that some people are and may always be obese and that doesn't mean they have to hate themselves.
Like thats all the movement really is- you are not worthy of hate because of how your body looks. And when people just have to shout over it with "but your soooo unhealthy" its missing the point.
But also body positivity isn't just about weight, it also includes things like disabilities and physical differences and scars. Just other ways a body might not fit the beauty standard. And many of those might also be relfections of a person not being 'healthy'. The people chiming in to nice positive posts about how your body doesnt define you with how 'it doesnt matter because that person is so unhealthy and it sends a bad message', just seems really shitty to me.
You can have your own conversation about the benefits of being an ideal weight loads of people are. I don't know why it has to be thrust on the one conversation about being kind to yourself and celebrating being positive about bodies.