A fundamental problem with the calorie balance view of obesity is that it considers all calories alike, regardless of source, in some obviously awkward ways. According to this view, a pastry and a peach would affect the body in the same way, so long as we consume them in the same amounts — violating basic nutritional common sense. If this were true, why would we need dietitians at all, whose primary job is to advise which foods to eat and which to avoid? Some calories seem to be more equal than others!
To get around this predicament, nutrition experts have come to rely on the notion of the empty calorie.
Sure, having too many soft drinks may not be advisable, as this thinking goes, but not because of any negative effects of sugar itself. The only concern is that added sugar — which lacks fiber, vitamins, minerals, and other essential nutrients — will take the place of other foods that contain more of these nutrients. This argument was succinctly stated in an editorial in the prestigious American Journal of Clinical Nutrition in 2014:
“As a card-carrying dietitian in good standing, I certainly am not going to tell people to eat more sugar. But we must be clear that added sugars provide 4 [calories per gram] just like any other digestible carbohydrate and are no more likely to cause weight gain than any other calorie source. The rationale to reduce intake of added sugars . . . is to reduce calories and thereby increase nutrient density.”
But are we really to believe that a cup of Coke would be as healthy as a large apple (both with about 100 calories), if we drank it with a serving of Metamucil and a multivitamin pill?
In fact, foods with similar nutrients can affect hormones and metabolism in profoundly different ways, determining whether we store or burn calories, build fat or muscle, feel hungry or satisfied, struggle with weight or maintain a healthy weight effortlessly, and suffer from or avoid chronic inflammation. These novel aspects of food, independent of “calorie density,” can be used to create a powerful prescription for weight loss and disease prevention.