The truth is we don't know the answer, best I can tell. I haven't fact checked this but I was having a conversation with someone the other day who said that no country has ever reduced their obesity rates, they have all gone up since we started recording it. What that tells me is a need for more studying, and trying different methods, because all the ones so far have been terrible. What we categorically do know, from multiple studies, is that shaming leads to more depressions and anxiety, which just makes people eat more.Fat shame is of course not the answer.
I don’t know what is though? It does cause misery and illness, and is in the hands of the sufferer to resolve (duly noted those who are dependant mentally on others rely on them to consider the diet of the person they care for).
It's probably also worth mentioning that it's not just that there are more morbidly obese people, but generally more overweight people, and this could simply be because people live longer these days, and we have an ageing population. The age group most likely to be overweight or obese is 65-74. It's clearly harder to be more active when you're older, and now thanks to modern medicine we have more old people. So a large part of this could just be the consequences of having more old people, who are going to have more health problems as a general rule.