Apparently new research suggests factors such as the softness of a food can have a significant impact on the ability of the body to convert the stored energy.  For example, two sets of rats fed the exact same calorie content, but one set was fed hard food, the other soft.  The rats receiving the softer food were significantly overweight compared do the other group.  Check out this fantastic read if you are watching what you eat:

http://www.newscientist.com/article/mg20327171.200-the-calorie-delusion-why-food-labels-are-wrong.html?DCMP=OTC-rss&nsref=online-news