I think it'd be more accurate to say that informing people that they should change their behavior doesn't work. A person changing their behavior can escape obesity. The reality is that most people won't be able to change their behavior without some other kind of assistance.
Even with extensive assistance (which is way too expensive to widely deploy) outcomes are weak.
Last I checked, researchers in the specific area of high-touch weight interventions were excited that they finally had a tool that might more-than-barely work… in glp-1 agonists.