Ever been told "all you need to do to lose weight is push away from the table and move more." Did that person live? Kidding.
Seriously though... anyone who is fighting this war on a personal level knows obesity is a complex multifaceted issue and more than the simple math of calories in, calories out. It it were that simple we wouldn't have 93 million Americans affected. Check out this great video that explains what causes obesity and why is it so hard to lose weight through diet and exercise.