DW was just commenting on that this morning. She was looking at old family photos from 1960's on and even with casual friends the obesity so common now just isn't there. All the kids are rail-thin, some of the adults might have a bit of a paunch but no one was obese.
So what happened? Can't blame it all on potato chips as we certainly had those then - just not much of it. Too many restaurant meals and meals out of boxes? Is it realistic to blame it on fast food? We so rarely eat out that I have little idea of what is "normal" for eating out.
This is one of those that is, IMO, an intersection of factors. A great deal of this relates to changes in the overall food environment. It is easy to say it is individual portion control and that is a factor but there is no reason that couldn't be a factor 50 years ago. I actually did a blog post a week or so ago talking about how eating was different "then" as opposed to now. Some of the factors:
1. Highly palatable food designed to cause overeating. I used to think this wasn't a major factor. I know think it is. A couple of books that are interesting on this are
Salt Sugar Fat and
The End of Overeating. These books are really fascinating about how. Here is a NYT article by the author of Salt Sugar Fat that talks about some of this:
The Extraordinary Science of Junk Food.
The point is that food is scientifically designed to appeal to people through the use of sugar (especially), fat and salt. There is discussed a concept of manufacturers spending lots of money to decide the "bliss point" of food which is the exact amount of sugar that people find the most appealing.
When we look back to 40 or 50 years ago, the techniques are crude in comparison to what they do now. Some of the stuff talked about in Salt Sugar Fat is how even some people in the food industry feel that they have designed food to be so appealing that this has led to the obesity crisis.
I am not saying this is the only factor. I'm not saying that personal responsibility isn't a factor. I would perhaps compare this a bit to smoking. Not smoking does involve personal responsibility and stopping can be very difficult. But, we also recognize that there is some responsibility on the part of cigarette manufacturer's so we put a lot of restrictions on tobacco (ie, warning labels, advertising restrictions, age limits, etc.). Those kinds of restrictions largely don't exist for unhealthy food that promotes obesity (such as sugared soft drinks for example).
2. Portion sizes. Back in the 1960s I was allowed to have a 6 1/2 oz. Coke a day, occasionally a 10 oz. Even when we rarely ate out, drink sizes were small and no free refills. A "Jumbo Jack" seemed huge then and would be tiny under the standards now.
3. More sophisticated advertising of food. The ads for food on TV now compared to how they were in the 1960s -- no comparison. Also more ads while out and about. Even the smells from the food court all make food very appealing.
4. People eating out more. A lot of this is because people are busier and more women are in the workforce and so more people eat out more often. Another factor, though, is that food eaten out is more appealing than it used to be. Back in the 1960s restaurant food was more like the food eaten at home and wasn't so appealing. In the End of Overeating there is a lot of discussion about restaurant food and how it is often way higher in calories than similar food made at home. It is often fried in a factory somewhere then frozen and sent to the restaurant and then fried again. The result is a food much higher in calories than most people would suspect.
Edit: On the issue of overweight people living longer than normal weight people, I read an interesting article that separated out stats based upon whether people were smokers or not. The gist was that smokers were more likely to be thinner, but would die earlier due to their smoking. So the presence of smokers skewed the data.
If you looked only at people who had never smoked, it looked like the lowest death rates were associated with being normal weight rather than overweight.
All right here it is -
http://www.runnersworld.com/weight-loss/why-im-not-sold-benefits-being-overweight
