In this installment of The Practical Scientist we take a look at Bray’s review of Good Calories, Bad Calories. Bray’s review is very in-depth and offers counter points to some of Taubes’ key assumptions. Bray’s review provides a key lesson in separating Fact from Fiction.
Key Points from Good Calories, Bad Calories Gary Taubes; New York: AA Knopf (Bray 2008)
“Good Calories, Bad Calories is a scholarly book that musters the evidence for the case against the high-fat hypothesis for heart disease, cancer and obesity and in favour of the carbohydrate-insulin hypothesis. The bibliography is robust and contains a wealth of information.
The book begins with Mr. William Banting and the diet he published in 1863 as a small pamphlet called ‘A Letter on Corpulence Addressed to the Public’. In this pamphlet, Banting described his dietary success with a low carbohydrate diet. The hostility that Mr. Banting aroused among the ‘medical establishment’ in the 1860s is reminiscent of some of the comments about popular diets that have come from the ‘medical establishment’ in the last half of the 20th century. The background work on energy expenditure in human beings from Antoine Lavoisier, Hermann Helmholtz, Robert Mayer Carl Voit, Max Pettenkoffer, Max Rubner and Wilbur Atwater is very nicely detailed by Mr. Taubes. In addition to these, there are many other descriptions of scientists and their work that make this book particularly fascinating to read. Good Calories, Bad Calories is divided into three main parts. The first part is a critique of the Diet-Heart hypothesis, and the idea that dietary fat was the principal culprit in the rising incidence of heart disease during the 20th century. From an analysis of published data and discussion with many leaders, Taubes concludes that the Diet-Heart hypothesis detracted from our understanding of the relation of diet to heart disease. As Taubes sees it, Ancel Keys played the role of major villain in selling the idea The second part of Good Calories, Bad Calories sets forth the ‘carbohydrate hypothesis.’ This hypothesis is Taubes’ basis for explaining the evils of the ‘nutrition transition’ that have afflicted countries moving from their traditional diets to the Western type of high-fat, high-sugar, high-salt diet. In the third part of Good Calories, Bad Calories, called the ‘Mythology of Obesity’, the author argues that the energy-balance equation does not adequately explain obesity because obese people do not eat more than lean ones, and because they can lose weight eating a large number of calories, provided that the calories are very low in carbohydrates – that is, high in protein and fat. In the section on ‘The Mythology of Obesity’ and the carbohydrate-insulin hypothesis, there is no mention of doubly labeled water, a sophisticated technique that has allowed us to ‘check’ on the accuracy of self-reports of food intake. Also missing is a discussion of the ‘nutrient’ balance hypothesis. These limitations may change the conclusions that are reached from reading Good Calories, Bad Calories.
Critique of Good Calories, Bad Calories
One summer I admitted a group of four overweight teenagers to our clinical research unit at the Harbor UCLA Medical Center and put them on a 1000-cal diet under direct observation. As expected, all of the girls lost weight and were delighted with the result. When they left at the end of the summer, one of the girls, who lived only a short distance from the hospital, wanted to come back to see us so she could continue to lose weight. We instructed her on how to keep a food diary. When she returned 2 weeks later, she had gained a few pounds. She showed us her diary, which was very neatly and carefully kept. The average daily food intake was about 300–400 kcal d-1. As she had lost weight eating 1000 kcal d-1 while directly observed in the hospital, we were skeptical of the accuracy of her outpatient recording. We instructed her again on keeping food records. She returned after another 2 weeks, having gained even more weight and with records still showing she only ate 300 kcal d-1 or so. There was an obvious discrepancy, reflecting the difficulty of keeping reliable records. It was thus clear that this girl was either kidding herself or trying to kid us about how much she was eating. We have subsequently had the opportunity to study weight loss in a number of subjects in both the metabolic unit and then on similar diets in an outpatient setting. Weight loss under observation is about 50% faster than with the equivalent ‘prescribed’ energy deficit in an outpatient setting. The difference is adherence to or compliance with the diet. Obesity is the result of a prolonged small positive energy surplus with fat storage as the result. An energy deficit produces weight loss and tips the balance in the opposite direction from overeating.”
Comments from Taubes Responses from Bray
Comment: The problem is the carbohydrates in the diet, their effect on insulin secretion, and thus the hormonal regulation of homeostasis – the entire harmonic ensemble of the human body. The more easily digestible and refined the carbohydrates, the greater the effect on our health, weight and well-being. Response: The problem is a positive energy balance persisting over an extended period of time, which may be exacerbated by high-fructose/high-fat foods and other environmental agents acting on genetically susceptible individuals.
Comment: Through their direct effect on insulin and blood sugar, refined carbohydrates, starches and sugars are the dietary cause of coronary heart disease and diabetes. They are the most likely dietary causes of cancer, Alzheimer’s disease, and the other chronic diseases of civilization. Response: There is no convincing evidence that carbohydrates are producing cancer, Alzheimer’s disease, type 2 diabetes, or coronary artery disease.
Comment: Obesity is a disorder of excess fat accumulation, not overeating, and not sedentary behavior. Response: Obesity is the result of a small positive energy balance occurring over time. The Laws of Conservation of Energy (First Law of Thermodynamics) do not tell us why this imbalance occurs.
Comment: Consuming excess calories does not cause us to grow fatter any more than it causes a child to grow taller. Expending more energy than we consume does not lead to long-term weight loss; it leads to hunger. Response: Consuming excess calories routinely produces obesity, and consuming fewer calories than your body needs produces weight loss. Comment: Fattening and obesity are caused by an imbalance – a disequilibrium – in the hormonal regulation of adipose tissue and fat metabolism. Fat synthesis and storage exceed the mobilization of fat from the adipose tissue and its subsequent oxidation. We become leaner when the hormonal regulation of the fat tissue reverses this balance. Response: Fat accumulation cannot occur without caloric intake exceeding expenditure. Fat deposits differ in their health risks: visceral fat is strongly related to heart disease and diabetes; subcutaneous abdominal fat much less so; and fat on the legs may be ‘protective’. These differences in fat locations partly determine the differences in life expectancy between men and women.
Comment: Insulin is the primary regulator of fat storage. When insulin levels are elevated – either chronically or after a meal – we accumulate fat in our fat tissue. When insulin levels fall, we release fat from our fat tissue and use it for fuel. Response: Insulin is needed for fat storage, but it is for the purpose of storing the ‘extra’ calories not needed for daily energy expenditure. Chronic elevation of insulin, as in insulinoma, has only a modest effect on weight – something else is needed for ‘obesity’ in addition to insulin.
Comment: By stimulating insulin secretion, carbohydrates make us fat and ultimately cause obesity. The fewer carbohydrates we consume, the leaner we will be. Response: Calories count. Fructose (HFCS or sugar) plus a modest- or high-fat diet enhance the risk of overpowering the homeostatic feedback system.
Comment: By driving fat accumulation, carbohydrates also increase hunger and decrease the amount of energy we expend in metabolism and physical activity. Response: The quantity of fat we eat in a day is less than 0.5% of the fat we have stored, and these changes in fat deposition do not lead to increased appetite, as they are hardly seen on the concentration of leptin and other adipose tissue-related peptides
I enjoyed the review. I liked the comment and response section of the paper the most. I have read reviews from various authors on this book and they all conclude that the book contains some good reading but also contains much NONSENSE. The key messages that Taubes promotes are nothing new. Many nutrition authors have suggested insulin causes obesity, calories don’t really matter, and carbohydrates make you fat and so on. Many of the readers of popular nutrition books seem to like the idea that there is something more to it than calories. They can’t believe what Primary Researchers have been telling them for years- CALORIES DO MATTER. Many book readers enjoy science fiction. Should we expect something when it comes to nutrition books?
G. A. Bray (2008) Good Calories, Bad Calories by Gary Taubes; New York: AA Knopf Obesity Reviews 9 (3), 251–263. Visit Jamie Hale’s site at www.maxcondition.com