I think the definition of HAES should be any personal health practice that is health-centric and weight neutral. So health is pursued through healthy habits and without an attempt to manipulate body size. Other than that I think that people’s prioritization of their health and the path they take to get there is up to them and any health care providers they choose to consult.
I think there is activism to be done around HAES, especially as it relates to access. Nobody is required to practice HAES or any other health practice, but if you want to practice healthy habits then there shouldn’t be barriers to that – you should have access to the foods you choose, movement options that you enjoy that are both physically and psychologically safe (so that you can, for example, go swimming at your gym’s pool without any fear of being shamed), and affordable evidence-based healthcare (so your doctor listens to you and gives you interventions proven to help your symptoms and does not bring up weight other than if there are unexplained gains or losses, or to prescribe a proper dose of medication.) There is tons of work and activism to be done around access and it’s really important work.
I don’t think that we should use HAES as a platform to do size acceptance activism because I think that we should avoid even the intimation that some level of health or healthy habits is required for access to basic human respect and the rights to life, liberty and the pursuit of happiness. There is absolutely NO health requirement to demand your civil rights. You don’t owe anybody “health” or “healthy habits” (especially not by their definition, and not by any definition at all.) You do deserve, and have the right to demand, respect and the rights to life, liberty and the pursuit of happiness in the body you have right this minute – whatever your size, health and dis/ability.