It's a lifestyle, the optimal basic lifestyle, the one were you don't shorten your life/healthspan by decades. It's how thing were intended to be really.
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
Lifestyle changes are essentially standard medical advice. There is nothing wrong with proposing diet and exercise.
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 fatties instead of simply judging and hating them.