It's likely the result of genetic, epigenetic, cultural, economic, and food system factors combined.
As for how it went from 10% to 60% (your numbers, idk if they're right) one piece of the puzzle is that in 1998 the definition of obesity was changed, which made MANY more people fall into the obese category who did not previously: http://www.cnn.com/HEALTH/9806/17/weight.guidelines/
Ahh for sure, that’s a demographically representative sample of the american population. /s
Yes people have gotten fatter. That’s a thing that’s happening. To me that’s evidence of systemic problems in our food supply, economic factors like poverty. None of which are reason to treat someone poorly for being impacted by that.
As for how it went from 10% to 60% (your numbers, idk if they're right) one piece of the puzzle is that in 1998 the definition of obesity was changed, which made MANY more people fall into the obese category who did not previously: http://www.cnn.com/HEALTH/9806/17/weight.guidelines/