ever hear of the term "comfort food" ?
Many women find comfort in eating certain things, when they've had a rough day. They are so emotional by nature (not a broad generalization, just a fact about many girls) that they turn to that tub of ice cream, or the cheese cake or what have you as a source of stress relief.
Also, I'm a firm believer that women on a whole are much more attuned to certain senses, espceially their sense of tase and smell... We guys for the most part don't get enarly as much pleasure from eating as they do.
Couple that with the fact that there is such an abundance of really tasy and equally unhealthy food available everywhere you look, and we get girls that are getting bigger and bigger.
Obeseity is an epidemic, for both men and women..... It's just alot easier for girls to fall into the trap, it seems.
Another thought is that, as men, we want to be the biggest and the strongest we can be so we take the necessary steps to ensure that we bulk up and get muscular. Every extra pound of muscle you put on will burn 50 extra calories a day.
Women aren't so inclined to get muscular because they want a feminine physic... and we like them, that way.