It's a common belief "the camera adds 10 pounds," making anyone in a photograph look heavier than they actually are. This is mainly caused by an optical illusion, along with personal perception.
I know why America and other developed countries are the fattest in the world.....it's because of the TV's! I just got a new samsung lcd tv and noticed it automatically distorts the picture and stretches the screen to 16:9, even if normally it's 4:3, so there's no black on the screen. That makes all normal looking people look like fat people. And it makes people watching tv think the normal way to look is to be fat, and they quit caring about how they look because everyone's fat....it's on tv.
I have at least 4 friends with 16:9 tv's, and they all view regular 4:3 tv on their screens as 16:9, even regular tv programs, thereby stretching everything widthwise and making everybody look fat on tv. The tv's can be set to view at 4:3, but they need to be set that way and even most tv companies don't recommend that view because of the black lines on the edges, and these people don't bother to mess with their tv's settings.
So everyone thinks that fat is the normal way to be. Think about it, in the 70's when there were just regular tv's, nobody talked about the obesity problem in America because there wasn't any, now it's everywhere. It's because of the TV's!