Well, they are proving that's not always the case. Wish it were. What they are finding is that eating natural foods (i.e. in close to its natural form, minimal processing) keeps the pounds off better than processed with the same calories (I forget where I just read that study, but google it sometime). In a sense you are right, but if one eats all sugary foods, where are the B-complex vitamins to burn them off? So the person gets lethargic (sugar low after a sugar high) and the body stores the rest as fat. If there are proper nutrients in the body, the person has more energy and guess what? He burns them off faster, even while "resting". So yeah, your simple equation works in a sense, but what happens is people really cut the calories, still don't lose (body goes into starvation mode perhaps due to poor nutrition to begin with), and then cut even more and yes, they eventually lose weight, along with illness, lethargy and so forth. Then nobody wants to live that way, so they "give up". Perhaps its not so much the weight as the health. Some people are bigger than others. I have 3 cats, all fed the same thing. One's a downright fatty, the other two are slim (they are siblings). Yes she can jump and run as fast as the others and is otherwise in excellent health for a 13-year-old cat. Cats only eat when they are hungry and she is not a piggy, and they are not conscious about body image. I don't know why people can't accept the same instead of being persuaded by this Babylonian system of thinness and hedonism.