The point is obesity or bad diet is assumed to be the cause of everything with little to no investigation, a lot of the time, when there could be many causes.
Two recent examples for myself - I went to the GP with sudden, excruciating knee pain. I was diagnosed with osteoarthritis without any examination or xrays, prescribed weight loss medication ( as a former ED sufferer), and denied pain medication even though I made it clear the pain was having an impact on my daily life and ability to do my job.
I did manage to get an x-ray and examination because I work in a hospital. There are no signs of OA. I had a Baker's cyst which had burst. It was caused by a sudden increase in activity when I started my new job and had nothing to do with my weight. Had I been examined, or even been asked a few questions that could have been diagnosed at the start.
I've been at the GP, Urgent Care, and A&E several times over the last few years due to incapacitating digestive pain. I've always been told it was due to eating fatty, greasy food. I don't eat fatty, greasy food. I don't even like the greasy, spicy curries one A&E Dr blamed. I don't like fried or spicy food. No one ever asked me about my diet.
I start one thread on MN and immediately people pick up on how much acidic fruit and raw veg I'm eating and advise me to cut down. I haven't had a single episode since. If I'd been asked any questions at all in the numerous times I've presented to A&E and Urgent Care begging for morphine, that could have been resolved years ago but instead Drs looked at my size and assumed I ate shit, refusing to believe me when I told them otherwise.
Weightloss would not have helped with either of those issues and remaining thin would not have prevented it.