I’m in general agreement. What may be missing in your argument: Isn’t it possible that obesity is a symptom, not a cause, of other health issues? Kendrick in one of his books uses the example of “yellow fingers”: We know know that smoking “causes” (or more honestly “greatly increases risk of”) lung cancer. Many smokers have yellow fingers. Yet it would be logically incorrect to say that yellow fingers cause lung cancer. This example is of course ludicrous. It’s meant to be. But the lesson is that people, even professionals, are not immune to flawed thinking.
Relevant to obesity, my reading suggests it’s most likely caused by poor diet. Here we run into problems! Many authors make a case that even official diet advice may be wrong: e.g. too much sugar and simple carbs. There may be science supporting one view or another, but there’s another angle. At large scale there is almost always a political angle. Turns out that sugar, corn, etc. are big business and have enormous lobbying power in governments. This has been true for a very long time. More recently we have the “ecological” lobby that wants to reduce animal farming and such. Desire to get more money, protect existing markets and/or obtain more political power is almost always at root of such movements.