Nonna, when I was in college, we had a nutritionist and exercise guru visit our sorority. One thing that he said that has always stuck in my head is that a calorie is a calorie and if you eat more than you burn you will gain weight. It takes 3500 calories to make a pound so if you eat 3500 calories more than you burn you will gain a pound even if those calories are from lettuce. I think their are two catches. First it would be just darn near impossible to eat that much of the lower calorie foods like celery. And second, if you managed to eat that much it still will do less damage to your overall health than, say, eating 3500 extra calories of chocolate or fried chicken.