I’ve finished reading Gary Taubes’ Good Calories, Bad Calories, which I found to be an excellent guide to what the science actually indicates about nutrition. Taubes is an award-winning correspondent for Science magazine, and spent five years accumulating the research for this book.
Criticisms I’ve seen on the web seem to focus on two themes:
- Taubes supports the Atkins diet and other low-carb diets, and since we all know that Dr. Atkins was a quack, Taubes must be too (or at least he must have some hidden agenda).
- Taubes sees Ketosis as a valid physiological condition, whereas many others question whether this causes strain on the liver, brain, or other systems.
With that, here is a chapter-by-chapter summary. If you find it intriguing, I suggest reading the book as there is a lot of evidence and information bundled in there that couldn’t make it out into my short summary.
Chapter 1: The Eisenhower Paradox
Eisenhower was obsessed with lowering his cholesterol and took extreme measures to remove fat and cholesterol from his diet. His blood cholesterol kept climbing, and he eventually died of heart disease. Heart disease was rare before the 1920′s, but this could be because people didn’t live long enough to die of chronic diseases. Ancel Keys’ hypothesis that dietary fat and cholesterol are linked to blood fat and cholesterol became mainstream dogma by the 1960′s. Keys cherry-picked data, and probably did not perform “good science”. George McGovern used Keys’ hypothesis for the basis of “Dietary Goals for the United States” in 1977, which has underlined government health policy ever since. This document also used USDA statistics for historical macronutrient breakdowns based on guesses and not reliable evidence that people before the 1900′s ate much more grain and starch. They may have been thrown off by the temporary decrease in meat consumption due to Upton Sinclair’s The Jungle, published in 1906. USDA statistics are reliable after WWII.
Chapter 2: The Inadequacy of Lesser Evidence
From the 1950′s onward, Keys’ hypothesis was taken as proven truth and assumed as such in further scientific studies. In 1962, blood cholesterol in the Kenyan Masai tribe was measured at extremely low levels despite a high-saturated-fat carnivorous diet. They also had high atherosclerosis, but low levels of heart disease calling that link into question. Keys wrote them off as being genetically different from Westerners. The Framingham heart study was heavily touted as supporting Keys’ hypothesis, but in fact showed little correlation between blood cholesterol and heart disease. Keys’ hypothesis is further broken down into three tenets: 1. Cholesterol levels predict heart disease risk. 2. The amount of saturated fat in the diet predicts cholesterol levels and heart disease. 3. Monunsatured fats protect against heart disease. The 1968 Minnesota Coronary Survey was the largest related experiment conducted, but the results were not published for 16 years because they did not support the Keys dogma.
Chapter 3: Creation of Consensus
The American Heart Association recommended polyunsaturated fats such as corn oil from WWII until the early 1970′s, when reports suggested a link with some cancers, despite the cholesterol-lowering effects of these fats. As a result, the government started recommending a broad reduction in fat intake (Dietary Goals was one major vehicle for this message). Political momentum stifled debate despite a number of studies showing contradictory evidence.
Chapter 4: The Greater Good
In 1986, the NIH declared a consensus on the Keys hypothesis, and the government did significant marketing to cut fats from the diet. The paleolithic diet was used as a justification for why we should eat low-fat, but the assumed diet (based on modern hunter-gatherer populations) was skewed because researchers did not take into account that the “cavemen” would eat an entire carcass, not just the lean muscle tissue. This oversight was corrected in 2000 and the paleolithic diet was amended to include a much higher protein intake, lower carbohydrate intake, and similar or higher fat intake to a modern Western diet. The Nurses Health Study conducted in the 1980′s demonstrated a link between saturated fat intake (with a corresponding decrease of carbohydrate calories) and reduced risk of breast cancer. The American Cancer Society continued recommending a limited red meat intake until 2006, when the lack of correlation between fat consumption and cancer risk was acknowledged. Studies in the 1980′s and 1990′s have demonstrated that very high cholesterol does increase the risk of heart disease in men under 50, but very low cholesterol is associated with increased risk for cancer and respiratory diseases. In women, higher cholesterol is not associated with any increased cause of mortality. Despite the government mandates (which people have followed), there has been no decrease in heart disease rates.
Chapter 5: Diseases of Civilization
Several populations (e.g. Eskimos and Gabonese) have negligible rates of chronic diseases such as cancer, diabetes, obesity, heart disease, and stroke when eating their native diet. When some members of those populations begin to adopt a Western diet their rates of chronic disease rise up to Western levels while their counterparts who maintain the traditional diet continue to be healthy. Meat-eating seems unlikely to be a cause of cancer as carnivorous Inuit and Masai have extremely low cancer rates, while the vegetarian Hindus had a prevalence of cancers (circa 1910). Refined carbohydrates such as white flour, sugar, white rice, and molasses appear linked to risk of cancer.
Chapter 6: Diabetes and the Carbohydrate Hypothesis
Diabetes is caused by an overtaxed pancreas (the pancreas produces insulin). Eating sugar and white flour produces insulin spikes, which exert the pancreas. In the 1930′s it was observed that in a number of civilizations, including Sri Lanka, Thailand, Tunisia, and China, diabetes existed only among the rich who eat European food and drink sweet wine. In India, the vegetarian Hindus had far higher rates of diabetes than the non-vegetarian Christians and Muslims. Cleave and later Yudkin suggested that diabetes, obesity, heart disease, gall stones, and periodontal disease are linked and are caused by consumption of sugar, flour, and white rice. This theory seems to fit anecdotally, but further experiments are needed to definitely prove it.
Chapter 7: Fiber
Cleave and Yudkin’s ideas were dismissed by the McGovern panel because they did not fit the standard dogma. Burkitt expanded on Cleave’s hypothesis to suggest that the problem wasn’t the refined carbohydrates per se, rather it was a deficiency of fiber (which is mostly removed during the refining processes). This hypothesis was immediately seized upon by the media, and Kellogg and General foods pushed bran and fiber. Public health authorities initially remained focused on the fat/cholesterol hypothesis, but eventually adopted the fiber hypothesis as well. Two large Harvard studies in the 1990s and another study published in 2006 demonstrated that consumption of fiber and of fruits and vegetables is unrelated to the risk of colon cancer. Although the media is slow to catch up, the scientific community today seems to agree that fiber does not prevent chronic disease.
Chapter 8: The Science of the Carbohydrate Hypothesis
Insulin is the primary regulator of the storage and use of nutrients in the body. The regulatory system dominated by insulin is connected to aspects of chronic disease: carbohydrate and fat metabolism and kidney and liver function. Fructose intake has increased significantly in modern times, and is metabolised differently from other sugars and carbohydrates. Salt intake seems to have only a minimal effect on blood pressure.
Chapter 9: Triglycerides and the Complications of Cholesterol
Rather than cholesterol being a critical component in heart disease, research has implicated the molecules that carry cholesterol through the blood: triglycerides and lipoproteins. Both of these carrier molecules are regulated by the carbohydrate content of the diet, not saturated fat. Cholesterol is made up of LDL (bad cholesterol), HDL (good cholesterol), and VLDL (carry most of the triglycerides). Saturated fat elevates LDL levels, but carbohydrates elevate VLDL levels. Measuring total cholesterol is not a good indicator of heart health risks because the measurement does not differentiate LDL from VLDL. A high HDL to LDL level helps protect the heart, and monounsaturated fats raise HDL and lower LDL. Ironically, the principal fat in red meat, eggs, and bacon is the same monounsaturated fat in olive oil. Stearic acid, the most prevalent saturated fat in steak, also increases HDL while having no effect on LDL.
Chapter 10: The Role of Insulin
Counterintuitively, diabetics have higher circulating insulin levels than normal people; their tissues are resistant to the effects of insulin so they need larger amounts either secreted naturally or via injections. Attempts to understand the relationship between obesity, heart disease, and diabetes have implicated chronically elevated insulin levels as a culprit.
Chapter 11: The Significance of Diabetes
Metabolic syndrome is related to diabetes. Both conditions carry elevated risk of heart disease. Elevated blood sugar results in the production of free radicals and other oxidants. In addition to the cardiovascular system, oxidants affect other tissues such as the skin, causing diabetics to appear prematurely old.
Chapter 12: Sugar
The development of the glycemic index (a measure of how quickly different foods affect blood sugar) supported Cleave’s speculations. Fructose has been shown to elevate triglyceride levels, and this effect increases with long-term consumption. Fructose-containing products such as table sugar and high-fructose corn syrup strain the liver and block the metabolism of glucose, which causes the pancreas to secrete higher levels of insulin to attempt to regulate the blood sugar; this combination of fructose and glucose causes a harmful feedback loop with more harmful effects than either sugar alone.
Chapter 13: Dementia, Cancer, and Aging
Metabolic syndrome, high blood sugar, and insulin resistance have many physiological repercussions that can conceivably explain Alzheimer’s disease and cancer.
Chapter 14: The Mythology of Obesity
The standard dogma that being overweight or obese is caused by excess calorie consumption and/or inadequate physical activity does not hold up to evidence and observation. Increased rates of obesity in the U.S. over the last 40 years correlate with increased carbohydrate intake and decreased fat intake. Pima indians living in the United States (on a diet high in refined sugars and starches) have rampant obesity, whereas those living in Mexico (eating their traditional diet) do not.
Chapter 15: Hunger
People on a starvation diet will lose weight, but they complain of constant cold (i.e. low metabolic rate) and hunger. When allowed to eat to appetite they will gain back all the weight they lost and more, resulting in a higher percentage of body fat than they had originally. In the WWII-era Minnesota study (overseen by Keys), post-experimental subjects weight 5 percent more than they had before the experiment and they had 50 percent more body fat. One exception is the extremely obese, who may respond better to a low-calorie diet (possibly they have a significantly altered metabolism). When excercise increases, the appetite will increase accordingly. Because heavier people have more body mass to support, it may be that obesity causes increased appetite not vice versa.
Chapter 16: Paradoxes
The distribution of fat on men and women suggests that sex hormones are involved as much as or more than eating and physical activity. Overfeeding experiments have shown differences of a factor of 3 in people’s ability to gain fat and general weight; most of this weight drops off when eating to appetite resumes. A single genetic defect causes obesity in rats, regardless of diet. Observational experiments show that overeating is not the cause of obesity.
Chapter 17: Conservation of Energy
Calories in minus calories out is based on misinterpretations of thermodynamic law. A false assumption is that the only variables to the body energy balance are food intake and exercise, omitting the body’s internal energy expenditure. Increased appetite and sedentary behavior may be effects of obesity, rather than causes. Protein has a thermogenic effect when eating in quantities beyond the amount necessary to maintain tissues and organs; this heat is another expenditure of calorie energy. Maintaining normal body temperature takes more energy on a cold day than on a warm day. When undernourished, the amount of heat and energy produced are reduced as the body must prioritize the use of nutrients. This will cause a gradual lowering of metabolism and a tendency towards reduced activity.
Chapter 18: Fattening Diets
Various tribes and sumo wrestlers induce fattening with high carbohydrate, low-fat foods (ironically, the same nutrient breakdown commonly recommended in the U.S. to lose weight). Experiments showing that rats on a high-fat diet became obese neglected to report that those rats preferentially chose foods high in both fats and carbohydrates such as sweetened condensed milk, cookies, and bananas. They did not eat to excess high-fat, low-carbohyrdate foods such as cheese, pastrami, and peanut butter. Rats, pigs, cattle, and monkeys all fatten when fed high-carbohyrdate diets.
Chapter 19: Reducing Diets
Low-carb diets are broadly considered to be “fad diets.” Many successful low-calorie diet observations may be explained by the corresponding decrease in carbohydrate consumption. If the body does not intake enough glucose to fuel the brain, the liver can synthesis ketone molecules and some additional glucose can be synthesized by breaking down proteins and triglycerides. Animal-based foods contain all essential amino acids in an optimal ratio for humans. While some plants (e.g. wheat) may contain all the essential amino acids, the proportions may be such that unrealistic quantities have to be eaten to get a sufficient amount of the scarcer acids. People on an all-meat diet have not been observed to have kidney damage, loss of energy, or vitamin or calcium deficiencies. Carbohydrates have been shown to deplete vitamins B and C, and inhibit the body’s ability to absorb more vitamin C.
Chapter 20: Unconventional Diets
In the 1950′s twenty overweight DuPont executives ate a high-calorie, low-carbohydrate diet and averaged a loss of 2 pounds per week without reported hunger between meals. Several experiments confirm that caloric intake does not inhibit weight loss if carbohydrate intake is low. Carbohydrates are shown to cause feelings of hunger, perhaps because the metabolism must be increased in order to process them.
Chapter 21: The Carbohydrate Hypothesis, I: Fat Metabolism
Obesity is caused by a defect in the regulation of fat metabolism; a disorder of fat accumulation, not overeating. Insulin plays the primary role in the fattening process; hunger and lethargy are side-effects. Carbohydrates – particularly refined ones – and possibly fructose are prime suspects in chronic insulin elevation. Racial fat deposits demonstrate that calories and exercise are not the causes of fat (or at least not the only cause).
Chapter 22: The Carbohydrate Hypothesis, II: Insulin
The movement of fat to and from the fat tissues have little to do with the amount of fat present in the blood. This movement is instead controlled by hormonal factors (such as insulin). Fat storage is a by-product of carbohydrate metabolism (burning glucose for fuel). Insulin is the only hormone that works to promote fat accumulation; eight others promote fat mobilization. Fat cells are more insulin-sensitive than other cells.
Chapter 23: The Fattening Carbohydrate Disappears
Robert Atkins developed and popularized the low-carb concept published by Edgar Gordon. Atkins has been kept on the fringe by mainstream nutrition scientists, but has shown effective results.
Chapter 24: The Carbohydrate Hypothesis, III: Hunger and Satiety
Experiments in rats have shown that they will develop tastes to make up for induced needs or gluts, for example salt when their adrenal glands were removed, or an aversion to carbohydrates when they were diabetic. Fertility is linked to the availability of metabolic fuels. The levels of circulating insulin are proportional to body fat. Sugars and carbohydrates have addictive properties.
1. Dietary fat does not cause obesity, heart disease or other chronic diseases.
2. Refined carbohydrates, through insulin secretion, do.
3. Sugars, especially those including fructose, are particularly harmful.
4. Refined carbohydrates are the dietary cause of heart disease and diabetes. They are the most likely (but not only) dietary cases of cancer, Alzheimer’s disease, and other chronic diseases.
5. Obesity is not caused by overeating or sedentary behavior.
6. Calorie restriction does not cause long-term weight loss, it causes hunger.
7. Fattening and obesity are caused by a hormonal imbalance, which can be driven by diet (e.g. insulin secretion).
8. Insulin is the primary regulator of fat storage.
9. Carbohydrate intake drives insulin, and is therefore proportional to our body composition.
10. Carbohydrates also increase hunger and decrease energy.