Aristotle observed that an object falls at a rate that is proportional to its weight. Heavy objects fall quickly, and light objects fall more slowly. Makes sense, right? For hundreds of years Aristotle’s word on this was so widely accepted as truth that there was simply no point in performing an experiment to verify or contradict it. Why bother? It was enough to say Ipse dixit, literally “he said it.” If it was good enough for the old man, it’s good enough for me. It took the righteous and contrary Galileo to proclaim what anyone who bothered could see: Look here! I drop a grape and an orange together and they fall at the same rate. This man Aristotle is either a fool or a liar.
When we look back at this episode, Galileo is always our friend. We sit next to him on the bench and chuckle. Grinning and pointing at the Aristotelian dopes, we ask him: How can all those people be so stupid?
Galileo is right not to be so impressed with us. Now as then, it happens all the time.
To choose a more recent example, why are Americans getting so fat? The answer is obvious. We’re rich, lazy, and overfed. Case closed. But the data doesn’t support the story. Exercise and caloric intake don’t correlate with weight gain. And perversely, sometimes malnutrition, poverty, and obesity appear to be best friends. What’s going on? Science writer Gary Taubes has taken on this important subject in his book Good Calories Bad Calories. Here’s a lecture of him talking about his book.
My brother Paul is an endocrinologist who is especially taken with the book. He talks about it all the time. He talks about it so much that I asked if he’d be willing to write about the book and why it matters. Happily, he agreed, and here is the result…
Good Calories, Bad Calories
by Paul Gulley, MD
Regarding Good Calories, Bad Calories and 35 years of probably bad dietary advice
“It’s no wonder that truth is stranger than fiction. Fiction has to make sense.”
— Mark Twain
Disclaimer- this brief article is an attempt to summarize a large volume and must be viewed not as definitive, but as a starting point. I would heartily recommend reading the entire book. It explains the science and the politics of current and past USDA/HHS recommendations, and how they have gone awry.
Often a book or an idea will turn your world and your beliefs, cherished beliefs, upside down. Suddenly everything you had counted on and all the advice you had given is shown to be if not false, at least tainted. Good Calories Bad Calories by Gary Taubes is such a book.
As an internist I try to advise patients with what I believe to be a healthy diet. Over the years the diet mantra has been low fat and low calorie along with exercise. And if a person did not achieve their goals then it was their fault, a failure of will.
This advice was based on the ubiquitous and what I thought was the well-researched Food Pyramid. The Food Pyramid had its origins with establishment of recommendations from the USDA. The original guidelines came out in the 1890s and have been revised over the years to tell Americans what they should and should not eat. The 1970s version of the guidelines came out of the McGovern Hearings with the dawning realization that cholesterol and fats were found to be elevated in people with coronary heart disease. At that time, the seemingly logical conclusion was made that fat on the plate equaled fat in the blood stream and fat in the gut. The recommendations flowed from several assumptions: 1) all calories are equal and are handled in the same way by the body, 2) thus eliminating a gram of fat, which contains 9 calories per gram, gives you a better return on investment than eliminating a gram of carbohydrate at 4 calories per gram, 3) fat calories are fattening and 4) exercising can burn up excess calories. The Food Pyramid emphasized low fat diet. There were some dissenting voices at the hearings, which thought that a causal relationship had not been established and recommended further studies. But these were voted down and the food Pyramid became the law of the land and the official advice given by doctors and dietitians (and it still is).
All food comes in three categories: fat, carbohydrate and protein; thus if you encourage a low fat diet then it will necessarily be a high carbohydrate diet. Over the last 35 years people have done what they were told and have consumed a relatively low fat diet. Every label in the grocery store screams “low fat” and “reduced fat.” But calorie consumption has increased – primarily in form of carbohydrates. Coincidently over last several years there has been explosion in the rates of obesity and diabetes.
Some basic physiology is necessary. Insulin is the key hormone in carbohydrate and fat metabolism. The pancreas produces insulin primarily in response to carbohydrate stimulus in the diet. Insulin then facilitates the uptake of glucose into cells. It also stimulates fatty acid production in the liver. Insulin then blocks the release of fat from the fat cells or adipocytes. So insulin is a double whammy for fat cells: it encourages production of excess fatty acids and inhibits the breakdown and release of fat stores from fat cells. So fat accumulates but it can’t be used.
So as our nation, encouraged by the recommendations of the USDA, forged ahead with the low fat diet, the epidemic of obesity and diabetes became inevitable. It was further pushed by the agricultural policies that encouraged the planting of corn and food science that produced massive quantities of high fructose corn syrup, which turns out to be a very potent stimulator of insulin.
How do we reverse course and try to reestablish balanced recommendations for how people should eat? We need to go back to the basics and study the effects of different diets on different populations. This had been recommended in the 1970s and had been voted down as needlessly expensive. This needs to be done because all of the insulin/carbohydrate/fat interactions are driven by genetics and we do not understand the genetics well. That is why there are people who seem to be able to be able to eat anything and not gain weight and there are people who almost literally have to starve in order to lose weight.
This explanation also helps in the understanding of obesity. Until recently obesity has been viewed as a failure of will. If only these people could control their appetites and exercise sensibly then they should be able to lose weight. But a more complete understanding seems to be that obesity is a genetic disorder of fat accumulation uncovered by exposure to concentrated carbohydrates (particularly sucrose and high fructose corn syrup). Also hunger seems to be driven by carbohydrate intake. So carbohydrates makes you hungry and fat.
Okay, what are we supposed to do until the population studies are done (if ever they are done)? The primary recommendations are to avoid concentrated carbohydrates- white things: bread, pasta, potatoes, rice and sweets. These are foods that stimulate insulin and begin the cascade of fat production and storage. Diet aficionados reading this may recognize these same guidelines in the Atkins Diet. In the late 1960s and the early 1970s Dr Atkins advised a low carbohydrate diet for weight loss. However a low carbohydrate diet is necessarily at high fat diet. In the 1970s fats were anathema to the gurus of the day and Dr Atkins was vilified and denounced in official literature as a quack. But this diet appears to be closer to the best recommendations. So it is not how much you eat but what you eat.
It seems probable that we all have a tolerance for carbohydrates that is likely genetic. Obese persons have a very low tolerance for carbohydrates and should try to avoid them altogether. Others can limit to achieve the goals of weight and metabolic parameters. I have not discussed glucose toxicity and the metabolic syndrome and its consequences for risk of vascular disease. But obesity is only one of the risks involved with carbohydrates.
Again this is a very complicated subject and much more can be said and is said in the book. The concepts of homeostasis and the pathology of the metabolic syndrome are discussed in detail. Importantly, the book also elucidates the politics of science and public policy. The book demonstrates that the obvious explanation just might not be the true explanation.
The whole question of diet and policy recommendations leads to a larger question of other “truths” that just might not be “true.” How and what is ”scientific certainty”? How do we establish societal “truths” for general consumption? These problems become concrete, as I have to explain to patients that the advice I have rendered for the last 24 years was not the best advice. Yet many still refuse to concede that the concepts are valid since they don’t make “sense.” As my father-in-law said when I tried to tell him that his cherished low fat diet might not be necessary, “I don’t care if it’s true, I just don’t believe it”
Finally, I want to convey the bewilderment this book awakened. Delighted by a fresh approach to the evidence I had thought codified and unchanging, I feel renewed. I hope others share in this same sense of wonder. It is good to be reminded that there is no such thing as absolute scientific certainty. Additional research may one day contradict the conclusions of this book, but that would be science working, as it should.