This is an interesting topic to read.
Obesity, weight, metabolism, etc. are all part of an incredibly complex system -- as complicated as the weather and maybe more so. One thing or another is not the cause, nor will it be the cure.
Just to throw a few more things out there.
1) People are living longer than ever before, and the US is, on average, older than it used to be (e. g. there are more people living longer and fewer babies being born). This contributes to an overall feeling that there are more overweight people when that's a byproduct of the fact that there are a lot more middle-aged and young old people -- and these folks tend to be heavier.
2) Smoking is down considerably in the last 20 years. The dirty not so secret secret is that nicotine (and the loss of the sense of smell from smoking) are appetite suppressants/oral substitutes. Eat something, even something very healthy, or smoke a cigarette? Smoking doesn't pack on calories, but even apples do.
3) High fructose corn syrup -- oh yeah, preach it. It is in everything, way more than ever before. Most of our food either contains corn or is a meat from an animal fed corn. It is everywhere in our diet, and it ain't helping things.
4) Also, good old trans fats, cholesterol, etc. Plus, like Slappy, etc. said, good old fashioned calories. Portions are huge. I'm not even talking about fast food. Go to the diner near us and you are served not on a plate but on a platter. This is not a rarity.
5) People eat out more because people are busier. They work long hours, chauffeur their children from tennis to soccer to chess club to wherever and they don't have time to cook. There's all sorts of junk hidden (and in plain sight) in restaurant meals and there's very little regulation. Go to Pizzeria Uno some time and check out thei nutritional information.
http://www.unos.com/kiosk/nutritionUnos.html This is typical.
6) Yo-yo dieting not only does not work, it makes things worse. A person of 140 lbs. who diets down to 120 can end up back at 160, then yo-yo down to 120 or 130 and then up to 190, all in a few years and not with a lot of slacking off when the weight goes back on. It's no great secret that it's a helluva lot easier to gain weight than it is to lose it. Many of us do the former extremely well and efficiently, even when not trying, but have a devil of a time with the latter, even when thrown into it 100%.
7) Lack of education is likely not the case for most overweight people. The message is all over the place so perhaps that strategy should be rethought. Telling someone to eat less or better, yet to not give them the means to do so (better choices in the school cafeteria; cheaper healthier food; put the nutrition of restaurant meals front and center; slow down our go-go lives so that people have a chance to cook, etc.), well, that's kinda useless, dontcha think?
8) I believe that set point has a meaning. That is, you get to a higher weight, your body kind of "gets used to" it (I need a better way to explain that) and it doesn't budge unless you really whip yourself. I have been the exact same weight for 3 years running, despite cooking at home 6 out of 7 days a week, watching the hell out of my cholesterol and walking a mile every day in commuting alone. I am not sitting at home eating bon bons and I cannot remember the last time I had fast food. As in, it was something like 10 years ago. My cholesterol, yes, has retreated. But my weight? Nope, it sits there, like a rock. So don't tell me I won't stop eating or I eat junk or I don't exercise or anything of the sort, or even that I was an overweight child, 'cause it ain't true. Do I need to do more? Absolutely, I do not deny that for one minute. But the point I am making is that a simple pronouncement of one type or another is not accurate. It's no more accurate than saying that a hurricane is the result of a 5 degree rise in temperature on one day in July. It isn't, it's due to the temperature, the humidity, wind, water, land mass and the price of tea in China for all anyone knows. Yes, we have a lot more info than we ever did, but there's a lot more out there, not yet known. I suspect we will find, among other things, that the corn syrup is killing us but also that there are several complicated genes controlling a lot of this or giving us dispositions in one direction or another. Too many calories? Of course. Not enough exercise? Hey, I'm on your page. But I think there's plenty more to be discovered in this area.
Oh and by the way, a quick pitch here. Personally, whatever you all think of the overweight, that's nice, whatever, but do, on occasion, think of what you are saying about your fellow human beings. Weight has become a fine place for people to park their prejudices. Name-calling, finger-pointing, blame-giving, yep, it's all there. So do, hold a little kindness for people, if you please, who are, it is likely, fighting an uphill battle and not just sitting around stuffing their faces every five seconds. And, as Bear has attested, get yourself bedridden for a short period of time, and you could get on this funhouse ride, too, yanno.