The answer throughout is always, always that it's a systemic problem and not the fault of individuals. The filmmakers and the experts they consult are extremely invested in making it clear that they don't hold individuals making "bad" choices accountable for this. Repeatedly, for instance, they point out that a person's BMI is surprisingly predictable based on nothing more than a zip code, which I thought was a nice, clear-cut way to get the audience out of the "personal responsibility" framework of utter meaninglessness, and move them towards the "collective responsibility" framework that actually suggests solutions. From there, we're treated to two episodes where food marketers, agriculture subsidies, conservative politicians, increasing work loads, and underfunded schools and communities are targeted as the cause of the problem. I was particularly interested in the emphasis on how overworked Americans are, which is an aspect that a lot of other writers on this issue don't look at. One in four Americans doesn't get any physical activity at all, and the reason pegged in this documentary is their jobs---between commuting to and from work and sitting at a desk all day, people just don't have time. Turns out that stress is a major factor in developing obesity, because being stressed out tends to override a lot of brain functions that prevent overeating. One expert talks witheringly of how stupid the concept of "free will" really is, and how it's a distraction from the real issues, which are that our society pressures you at every turn to eat more and exercise less.
Positive feedback loops are bad.