I wonder how much of the obesity increase in the US can be explained by the sheer fact that the narrative has become that it’s impossible to lose weight or to be different than you are, that it’s all fate and genes?

Though that’s not (mostly) directly propaganda, it is propaganda-like and therefore very effective at altering mental states permanently of those persistently exposed to it. This must have some effect. I don’t know that it’d be at all possible to tease out this effect with unbiased studies, but I’d guess it’s a pretty large one.

As an estimate, especially in the latter stages, I’d posit that 30% to maybe as much as 50% of the change in obesity levels can be explained by the near-propaganda of the “it’s impossible to change anything” narrative.