I don't think gluttony is the reason many people are overweight. Some yes, but not all.
I think it has more to do with the fact that the standard American diet is horrible and most people, including the USDA, have no real clue what a healthy diet is.
Plus, once you are overweight, and have damaged your body's metabolism, you do not have to overeat to remain overweight.
It's easy to point fingers, but it's a complex issue, and I believe different solutions are needed for different people/body types.
And just for the record, my BMI falls within the normal range.