Monday, December 12, 2011

Book Review: Good Calories, Bad Calories

For decades we have been taught that fat is bad for us, carbohydrates better, and that the key to a healthy weight is eating less and exercising more. Yet with more and more people acting on this advice, we have seen unprecedented epidemics of obesity and diabetes.

Gary Taubes, a correspondent for Science magazine, contributed to the Atkins Diet craze with his New York Times article several years ago, "What If It’s All Been a Big Fat Lie?." He then spent the past several years expanding on that article, and the result is Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease, a book of some 600 pages (nearly 70 of which make an extensive list of references).

In this book, Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease, Taubes argues persuasively that the problem lies in refined carbohydrates (e.g., white flour, sugar, easily digested starches) and sugars. He states that refined carbohydrates do harm via their dramatic and long-term effects on insulin, the hormone that regulates fat accumulation, and that the key to good health is the kind of calories we take in, not the number. There are good calories, and bad ones.

Good Calories
These are from foods without easily digestible carbohydrates and sugars. Examples in include meat, fish, fowl, cheese, eggs, butter, and non-starchy vegetables. Taubes claims that these foods can be eaten without restraint.

Bad Calories
These are from foods that stimulate excessive insulin secretion and so make us fat and increase our risk of chronic disease—all refined and easily digestible carbohydrates and sugars. The key is not how much vitamins and minerals they contain, but how quickly they are digested. Therefore, apple juice or even green vegetable juices are not necessarily any healthier than soda.

Examples of "bad calories" according to Taub include bread and other baked goods, potatoes, yams, rice, pasta, cereal grains, corn, sugar (sucrose and high fructose corn syrup), ice cream, candy, soft drinks, fruit juices, bananas and other tropical fruits, and beer.

Major Critical Points of Good Calories, Bad Calories
Taubes has several overarching themes. He contends, for example, that eating refined carbohydrates is what makes you obese, and that refined carbohydrates contribute to many of what used to be called "diseases of civilization" such as heart disease, which seems to have been less common in traditional cultures that ate less processed food, including Northern cultures that ate almost exclusively meat. (These arguments are still controversial, although new evidence continues to support them.)

With precise references to the most significant existing clinical studies, he convinces us that there is no compelling scientific evidence demonstrating that saturated fat and cholesterol cause heart disease, that salt causes high blood pressure, and that fiber is a necessary part of a healthy diet. Based on the evidence that does exist, he leads us to conclude that the only healthy way to lose weight and remain lean is to eat fewer carbohydrates or to change the type of the carbohydrates we do eat, and, for some of us, perhaps to eat virtually none at all.

Overall, this groundbreaking book, the result of seven years of research in every science connected with the impact of nutrition on health, award-winning science writer Gary Taubes shows us that almost everything we believe about the nature of a healthy diet may be wrong.

How Does This Book Relate to Animal Endocrinology?
It is obvious that many aspects of nutritional biochemistry and metabolism involve endocrinology and metabolism (regulation of insulin secretion and fat production). Remember that we as humans are also animals, and as omnivores, our nutritional needs are fairly close to dogs and other omnivores. Cats, on the other hand, are obligate carnivores, so their nutritional needs are quite different (i.e., high protein requirements but no need for carbohydrates at all).

This book also emphasizes the importance of nutrition as part of treatment of all endocrine disease, as well as all medical disease in general. The nutritional content of food has been something I have been focusing on recently, both for myself personally and also as a veterinary endocrinologist interested in furthering my understanding of animal health and medicine. Taubes' work in this field has been both compelling and eye-opening, and I am now thinking more critically about the unnecessarily high carbohydrate content of pet food (especially for the carnivorous cat).

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