umm.... you are deliberately comparing unrelated conditions to claim that excess weight doesn't affect health while ignoring all the ways where weight DOES affect health. a person who eats healthy meals and exercises but doesn't abuse alcohol, etc? is going to be healthier then the person who DOES NOT eat healthy and doesn't exercises. heavier person is more likely to develop joint issues, if they are fat rather then extremely muscled - they are going to have more visceral fat in addition to subcutaneous fat and why is that important? because visceral fat is the fat on organs themselves and that impedes their proper function in multiple ways.
https://www.health.harvard.edu/stayi...m-at-belly-fat
the older you get, the more adverse the effects are and the older you are, the more challenging it becomes to work up to healthier state. quality of life begins to suffer.
have you ever wondered why all the fat acceptance advocates tend to be under 30 and as soon as some of those start going into mid thirties and older, they suddenly change their lifestyle, start eating better, exercising more, losing weight? if you actualy listen to them, its not about the looks. its about their choices catching up to them.
P.S. there IS a major issue with a good number of doctors refusing to look deeper and resorting to "just lose weight" when faced with obese person and not every condition is related to obesity. and this bias IS a problem. but a good number of issues CAN be alleviated with a lifestyle change that just happens to result in weight loss along the way.