I think that your sentiment about “fat” people is true about 80-90% of the time around the world. Though I have heard that some places literally have “food deserts” in which supermarkets don’t really exist, or the ones that do might not stock healthy options. And in other situations some folks might only be able to afford (financially or executive-functionally) unhealthier options that might either take less time to select or prepare, or cost less money or driving time to procure. I think that’s probably where the downvote is coming from is people who feel unable to escape obesity due to a variety of limiting factors in their day-to-day lives which inhibit them from taking preliminary steps. not to say that going on a walk or taking the extra effort is not within their control, but that some people still struggle with it anyways, sometimes for reasons that seem counterintuitive or like that they should not be a real issue to deal with in practice but wind up being so anyways for some people who have never learned ways around the problems (or haven’t tried all or perhaps any of the different options yet) that they are dealing with.

there have also been decades-long propaganda campaigns by various lobbying groups to sow misinformation about dietary recommendations which leave me a bit more sympathetic to people who fall for the promises of various fad diets which sometimes go around in certain populations, (keto, paleo, plant-based [for health {separate in my perspective from people who legitimately decide for themselves to go “vegan for the animals”}] , fasting schedules [again for health reasons, I know religious fasting also to have a different meaning and origination of intention/purpose for lots of people], etc.)