This causes mental health issues to go unaddressed, but, ironically, it also helps in a way, because peer pressure certainly helps reinforce individual discipline to develop techniques to keep it together. Peer pressure is a very powerful motivator.
For example fat shaming is certainly bullying but it's also certainly effective at discouraging overeating
As far as I know, it just traumatizes people and discourages them from eating in front of the people shaming them. Then, as we all do, they relieve the trauma by using their usual coping mechanism - in their case, eating.
It's just like hitting kids. It teaches them to avoid getting hit; they learn nothing about their behavior.
But if you materially get fat you will get fat shamed regardless. So while it doesn't make you stop eating garbage, you will somehow, someway figure out how to keep a decent figure. This can either be exercise or more awful methods like surgery.
What makes you say that? Lots of people remain overweight, lots of research shows that shaming doesn't have the impact you say.
Also, lots of people can't physically do anything about it.
I think you should back that statement up with a citation.