We dance around it and call it 'obesity' but the real medical cause of obesity is an addiction to unhealthy food.
This is compounded by the fact that it is completely legal for people to make their food more addictive and therefore unhealthy and advertise it to addicted people with underhanded marketing techniques that take advantage of their addiction.
Until we recognize this as an addiction issue that is compounded by dealers being able to operate with impunity we won't make any headway -- short of technological advancements like Ozempic that allow people to side step their addiction.
As in, inability to keep them long term is biological defense of organism that does not have genetic predisposition toward anorexia.
Says who? Are you implying that true societal shame is still being enforced right now, without hundreds of refuges in the form of safe spaces and social justice advocacy groups? I'm pretty sure that such shame worked pretty well in the past, and still does in countries like Japan.
In the end, you'll just have to realize that the root issue you're facing is decadence, and that's there's no fighting it.