Wide Screen Effect
The so-called "obesity epidemic" in North America is caused by "wide format" LCD displays.
Let me explain: wide format television (16:9 aspect ratio) and computer monitors (e.g. 1280x800 pixels) are not yet universal, so most broadcasts and display drivers assume the old format (4:3 or 640x480). This technical stuff is too complicated for the 7-minute attention span folks, who only know that their TVs don't work right. Either the 4:3 image is shown with blank border stripes on the sides or the top and bottom are sliced off or (usually the default) the 4:3 image is just stretched sideways to fill that 16:9 screen. Either because they hate to "waste" any of that big new screen or because "it came that way" and they have no idea how to adjust it, most people leave their TV or monitor in "stretched" mode, distorting faces and text accordingly so that circles look like ovals and squares like rectangles.
I personally find this extremely annoying, but I have now had enough proprietors inform me with a straight face that, "Ain't nothin' wrong with that TV," that I have to believe they mean it. The implications are staggering.
It has long been known that most of "seeing" goes on in the visual cortex of the brain. When I had an "acute posterior vitreous detachment" in my eyeball (if you don't know what this is, just wait; you'll find out) the opthamologist said I'd have lots of big "floaters" but eventually my brain would learn to just ignore them. This seems to be true. Also, I once heard of an experiment in which people wore helmets with optics that turned everything upside down. After about two weeks their visual cortices adapted so that this seemed perfectly normal to them. When they took the helmets off, it took about two weeks to adapt back. This may be an apocryphal story, but if it's true, then merely adapting to a stretched TV screen should be a piece of cake.
But wait. The visual cortex must get confused when you go to the fridge to get a beer. The can looks all skinny. Either that or the people on the TV look fat; you can't have it both ways, unless you have an unusually flexible visual cortex.
Since most North Americans spend more time looking at a TV screen and/or a computer monitor than they do looking at the real world, it's obvious which side wins. After a while the stretched format becomes normal and the world looks tall and skinny. This is an unacceptable situation. What can be done?
Well, the solution is obvious: real people need to look more like the folks on TV. And so they do, exhibiting the magnificent adaptability that has allowed homo sapiens to survive environmental catastrophes that should have exterminated us long ago if there were any justice.
So that explains the "obesity epidemic". It is a collective social adaptation to prevent cognitive dissonance in the visual cortex. Switch back to the 4:3 aspect ratio on TV and computer monitors (or standardize on wide-format broadcasts and display drivers) and you will see everyone get skinnier again.
