The problem with this is that being overweight/fat exacerbates most (all?) chronic health problems, and often makes the treatments work more poorly or not at all.

The Fat Acceptance movement harms many, many more people than it helps or will ever help. If you have a chronic illness, in almost all cases it will benefit you to not be fat. I am sorry (a little) if brute facts hurt people’s feelings, but that’s no reason to stifle them. It’s better to have feelings hurt than to allow people to believe harmful feel-good rhetorical nostrums.