Good Calories, Bad Calories

The institutionalized vigilance, “this unending exchange of critical judgment,” is nowhere to be found in the study of nutrition, chronic disease, and obesity, and it hasn’t been for decades. For this reason, it is difficult to use the term “scientist” to describe those individuals who work in these disciplines, and, indeed, I have actively avoided doing so in this book. It’s simply debatable, at best, whether what these individuals have practiced for the past fifty years, and whether the culture they have created, as a result, can reasonably be described as science, as most working scientists or philosophers of science would typically characterize it. Individuals in these disciplines think of themselves as scientists; they use the terminology of science in their work, and they certainly borrow the authority of science to communicate their beliefs to the general public, but “the results of their enterprise,” as Thomas Kuhn, author of The Structure of Scientific Revolutions, might have put it, “do not add up to science as we know it.”

Though the reasons for this situation are understandable, they offer scant grounds for optimism. Individuals who pursue research in this confluence of nutrition, obesity, and chronic disease are typically motivated by the desire to conserve our health and prevent disease. This is an admirable goal, and it undeniably requires reliable knowledge to achieve, but it cannot be accomplished by allowing the goal to compromise the means, and this is what has happened. Practical considerations of what is too loosely defined as the “public health” have consistently been allowed to take precedence over the dispassionate, critical evaluation of evidence and the rigorous and meticulous experimentation that are required to establish reliable knowledge. The urge to simplify a complex scientific situation so that physicians can apply it and their patients and the public embrace it has taken precedence over the scientific obligation of presenting the evidence with relentless honesty. The result is an enormous enterprise dedicated in theory to determining the relationship between diet, obesity, and disease, while dedicated in practice to convincing everyone involved, and the lay public, most of all, that the answers are already known and always have been—an enterprise, in other words, that purports to be a science and yet functions like a religion.

The essence of the conflict between science and nutrition is time. Once we decide that science is a better guide to a healthy diet than whatever our parents might have taught us (or our grandparents might have taught our parents), then the sooner we get reliable guidance the better off we are. The existence of uncertainty and competing hypotheses, however, does not change the fact that we all have to eat and we have to feed our children. So what do we do?

There are two common responses to this question, as there will be to the arguments made in this book. One response is to take into account the uncertainties about the health effects of fats and carbohydrates and then suggest that we simply eat in moderation. This in turn implies eating a balanced diet in moderation. “Perhaps our most sensible public health recommendation should be moderation in all things, and moderation in that,” as the University of Michigan professor of public health Marshall Becker suggested back in 1987. But some of us do eat with admirable restraint of the four major food groups and yet are obese or overweight anyway, and presumably have an increased risk of other chronic diseases because of it; some of us are suitably lean, eat balanced diets in moderation, and exercise regularly and yet are insulin-resistant and maybe even diabetic.

The more optimistic response is a compromise position: to take virtually every reasonable hypothesis from the past fifty years that can coexist with the saturated-fat/cholesterol hypothesis of heart disease and fold them all into one seemingly reasonable diet that might do us good and probably won’t do harm. Thus, the current conception of a healthy diet is one that minimizes salt content and maximizes fiber; has plenty of good fats (monounsaturated and omega-three polyunsaturated fats) and minimal bad fats (saturated fats and trans fats); has plenty of olive oil and fish, and little red meat, butter, lard, and dairy products. When meat is consumed, it’s lean, which keeps saturated-fat content down and reduces energy density and thus, supposedly, calories. Dairy is low-fat or no-fat. The diet has plenty of nuts and legumes and good carbohydrates, which are those with copious vitamins, minerals, antioxidants, and fiber (vegetables, fruits, and unrefined grains), but few bad carbohydrates, which are energy-dense and thus contribute to obesity (highly refined carbohydrates and sugars).