http://www.physorg.com/news105804376.html

In pairs that don"t match, I wonder if there is any correlation between perceived body fat. For instance a woman who thinks she has a higher BMI choosing a mate with a higher BMI.

Thinness suggests youth, virility, fertility, health, etc., which means a greater probability of successful reproduction. Therefore there is competition for thin mates (ask any Hollywood exec/producer), and thus less likelihood that you'll find fat-thin couples and more likelihood of finding thin-thin and fat-fat couples.

In many cultures around the world (african, asian & pacific), being thin is associated with malnutrition, whereas a little fat is regarded as a sign of good health, and is generally thought attractive.

"This may be contributing to the obesity epidemic since it implies that overweight people will choose a partner who is also overweight, and so they will pass on to their children a double dose of the genes that have made them susceptible to being overweight or obese. "

Wow! That's really scary how many people have mutated/evolved to have "fat genes" in the last 100 years! Of course I am sure that it is ALL genetic and NOTHING to do with lifestyle, lack of exercise, and eating habits.

Seriously, how many people are actually overweight due to genetics that a moderate amount of exercise and reasonable eatings habits wouldn't have prevented? Quit blaming everything on genetics and point the finger at personal responsibility.

I agree with Icester that genetics couldn't play a major role in the recent obesity epidemic. For example I remember a study between the 80s and the 90s rates of obesity doubled and hyper-obesity tripled which is much too fast an increase for genetics to play a significant role. While an individual must accept personal responsibility for lifestyle habits if they want to maintain their health I don't think that pointing the finger at overweight people and telling them that it's all their fault is helpful or accurate.

So what's going on? I see a few major factors here:

Increased reliance on processed foods
Because of the economic realities of modern life people spend more time working than they used to which means they have less time and energy for other activities including cooking. Many deal with this problem by eating more prepared foods either from restaurants or prepared dishes bought at grocery/convenience stores. Another byproduct of working longer hours is stress. When people are stressed they tend to go for "comfort foods" which are high in fast carbohydrates and fat. Let's face it, when you've had a bad 12-hour day at the office ordering pizza sounds like a really great idea.
Highly processed foods have more calories for their volume, which means you can get more calories in before feeling full. They also are less nutritious and are processed by the body more quickly so you feel hungry again sooner.

Portion Inflation
Food has become cheap to produce. Since the bulk of the cost of food is now packaging and distribution you can increase portion sizes dramatically with minimal impact on the cost. We can see this in the "Super-size" phenomenon. I remember as a teenager 20-25 years ago that when you went to the convenience store the fountain drinks would be available in 8, 16 and 24 oz sizes. Nowadays the smallest size is 16oz and the largest are 60oz or more. If hunger was governed by the number of calories you consumed then this wouldn't be a problem. You would just eat larger portions less often. Unfortunately, people eat what's in front of them. For example: a study was done recently where one group ate from a normal soup bowl and another ate from bowls that were being refilled by a hidden tube. The refilled group ate an average of 73% more. See www.eurekalert.org/pub_releases/2005-04/uoia-iyf040405.php

Poverty
Anyone who has tried to eat healthy on a budget knows that eating nutritious food is more expensive. You can easily get a days worth of calories with a big bag of potato chips and a bottle of pop or several packages of instant noodles for $2. When you are on a very limited budget this is very attractive as it allows you to get the requisite number of calories to survive on a small budget. Although caloric needs are met or exceeded, nutritionally it's a disaster. So we end up with a large population of malnourished obese people. Malnutrition has been linked to poor cognitive development which leads to lower levels of education and success which feeds the cycle of poverty.

Lack of Physical Activity
I suspect that there has been a reduction in the average amount of physical activity during this time as well because there is less manual labor jobs than there used to be and that more leisure time is being spent on sedentary activities, but that's just a hunch.

Looking at all this I would pin most of the blame here on the food industry and the government bodies who regulate them. This is just beginning to be recognized with food labeling, the increasing regulation of the use of trans fats and efforts to keep junk food out of schools as examples of this new awareness. Hopefully in the future there will be more regulation in this area much like what was done with the tobacco industry as they are also selling a product that is detrimental to the health of their customers. Ultimately the only ones who can solve the problem are the consumers who must lobby their governments to restrict the activities of the food industry and who must vote with their wallets by creating a greater demand for more nutritious and less processed food.