When you look at how strongly obesity correlates with everything from back- and knee pains to weakened immune response to sleep issues and cardiovascular disease…

When a severely obese person has any of the above, it’s reasonable, scientifically backed diagnosis/prescription to say “these issues will probably go away by themselves if you lose weight”. This is about treating the cause and not the symptoms: When severely obese people are heavily over-represented among those with a certain disease or problem, you can try treating the symptoms, but should expect that they return rather quickly.

Of course, there are cases where the issues come from something else, but no matter who goes to the doctor with health issues, their first response will be to try to treat the post probable cause.