Your body follows your mind.
WLS does not update your identity, and if you have spent years or even decades struggling with eating and your weight, there’s a high chance that you still have the old fat identity (failure, sabotage, workarounds etc).
If you don’t update your identity to match your body, it can just be a matter of time until your body matches your identity. This is a key reason why I see patient’s regain their lost weight after surgery.