I agree there's probably a significant component of the tendency to gain weight, and once gained, how it's carried, that's genetic. Our shapes run in families. But were our families this fat before white sugar and high-fructose corn syrup hit the menu? Across the United States, at least, the answer is No or else the surgeon general wouldn't be concerned about the outbreak of obesity. This is new to us.

Pretty hard to control for variations in diet across generations. My grandfathers would not recognize most of what's in the grocery store today as food. (And quite possibly, many of the people in grocery stores today would not recognize the original form of most of those food products.)