Good point, Eva!

I don't think that there is any one cause of the obesity epidemic that we are currently seeing. Increased availability and affordability of junk foods, increased portion sizes, decreasing activity levels all play a part as well as the insulin resistance that a high carb diet promotes.
Interestingly enough, exercise does help decrease insulin resistance but there comes a point where even exercise can't overcome the high levels of carbs and you start seeing all sorts of things go haywire in the body...heart disease, diabetes, high blood pressure, bloodwork off kilter, etc...with or without weight gain.
I was just watching a program on PBS tonight where they had a fairly young (30-something) guy having a treadmill test. He was thin, fit and ran marathons as a hobby. His problem? High cholesterol and they were testing him for heart disease.