"The short version: If you're not forced to skip meals and not forced to sweat your ass off just to put food on the table, you're going to have a surfeit of calories, and neither your metabolism or hunger mechanism got the memo."
In the 1950s the US was not in the dark ages. We did not have to sweat our butts off just to put food on the table. We enjoyed a huge wave of prosperity. And yet, as a nation we were thinner.