You’ve all touched on the answers to the question. I agree that a lot of it has to do with psychological/mental issues (stress, emotional substitution, addiction), but there is also the fact that restaurants and eating out as a habit have both increased over the last few decades. While there have been restaurants for hundreds of years, eating out on a frequent basis has only become a custom for many families in the post-war years. This rise, in tandem with a decline in exercise and outdoor activities, has contributed to the imbalance in nutrition and weight issues that we see now.
I think a lot of it has to do with car culture; we’ve always had urban areas and sedentary people, but people used to be far more active when they had to use their own two feet to power transportation. Now that we can just hop into a car, whip through the drive-through, and head home to cocoon (whether it be video games, work from the office, movies, TV, or even Fluther grin), we don’t get out and stretch our legs and burn off energy like we used to.
Additionally, the increase in portion sizes has skewed perceptions of what’s “normal.” A kid’s meal at McDonald’s today is what a typical meal size was like at the same restaurant 50 years ago. The behemoths they serve today weren’t ordinary items on menus until about 20–30 years ago, and have just gotten worse since.
Finally, nutritionists and other experts have cast as culprits all kinds of foods. This leads to people throwing up their hands, and figuring that at some point, whatever’s bad for you is going to be good for you anyway. Throw in the various fad and boutique diets over the years, and our tendencies as humans to give in to the temptations of the siren calls emanating from the fridge, and it’s no wonder people eat too much.
The secret, though, is carbs. By themselves, in reasonable portions/single servings, they’re important elements of our diets. But eat too many, and they throw our systems out of whack. @wundayatta, while I agree cheese has fat, it’s actually not as dangerous as items with tons of carbs. I love cheese; I’d die without it. I have cheese at every meal. But by limiting my portion sizes of everything and keeping carbs to an absolute minimum, I keep my weight, cholesterol, and other levels at normal.
That’s just me though, and what works for me may not work for you. I’m not a nutritionist, and I’m far from an expert. Feel free to disagree, or add to what I have to say.