Hmmm. You all may right. To me, the change happened fairly quickly. Everytime I returned for a visit everyone thought I had lost a lot of weight (which I had not) but in reality they were all growing bigger. Living abroad protected me. When I finally moved back to the US in the late '90s, OMG it was super easy to gain weight here. I have to watch what I eat and exercise to keep it off.
Whatever is causing this obesity needs to be fixed because countries have been growing sicker.