Dr. Lipman: You say in your book that obesity is not from eating too many calories or expending too few. Can you explain? Dr. Fung: Obesity is often considered a problem of excessive calories. This caloric obsession has been indoctrinated into all of us since we were children. Too many calories in, too few calories out, or some combination is what we believe leads to weight gain and obesity. If it were indeed true that excess calories leads to weight gain, then the solution is simple: Reduce calories eaten. This has formed the standard dietary advice of the last 50 years. And it has failed spectacularly. Obesity rates have skyrocketed upward despite continual exhortations to cut calories.