> The idea that a cultural group could lose its ability to deal with such a key psychological and biological necessity in a short period of time just seems far less likely to me than a change in habits brought about by industrial and socio-economic circumstances.

But those industrial and socio-economic circumstances also had a huge impact on culture! It's super complicated!

I am not strongly anti-capitalist, but consider the impact of capitalism on food:

Take low cost ingredients. Put them together in an appealing way. Sell the product at a relatively low price (higher than the ingredients, but not much). Advertise the product widely in such a way to condition people to desire your product.

I am describing junk food of course. Walk into a convenience store or look at the checkout lines of a grocery store. Look at all the food you are conditioned to desire.

edit: I am not blaming capitalism as the single cause of obesity. There is much more to it than that.