Obesity rates started soaring only in the later 20th century. I'm suspicious of explanations for recent and rapid upward obesity trends that cite our evolutionary history from before the Neolithic Revolution. Human genetics did not undergo a massive shift in the last couple of generations. We did not just recently transition away from nomadic hunting lifestyles either.
No single factor seems to line up with increasing obesity rates well enough to be blamed as The Cause. I think it may be a combination of small nudges that form strongly obesity-promoting environments.
Marketing for unhealthy foods is a 20th century thing. And marketing something as healthy when it's actually not (fat free craze of yesteryear). To me it seems this is one of the major problems. Lack of education on healthy eating, damaging advertising, and a lack of regulation around food labeling.
No single factor seems to line up with increasing obesity rates well enough to be blamed as The Cause. I think it may be a combination of small nudges that form strongly obesity-promoting environments.