It's funny how proposing an healthy diet is unrealistic and watching fatties eat themselves to death is the new normal, complete value inversion and looser mentality
It's just that you should probably suggest other treatments in addition to the lifestyle changes that have relatively low long term efficacy.
Of course, that assumes your goal is to actually help the fatties instead of judging them.
Behavioural changes work, the issue is that most people don't actually change their behaviour.