The amount of calories needed to produce a noticeable change in body weight, up or down, is very small—a notion that also sidetracks our emphasis on calories. A difference of fifty calories can be difficult to distinguish in the context of a day’s total food intake; it’s equivalent to an average of less than a teaspoon of oil per day. Yet a difference of fifty calories retained by the body per day can theoretically cause a gain or loss of five to ten pounds of body weight per year.9 The problem is that consumption of calories does not equal retention of calories; retention of calories is not something we can consciously control by counting. So, in this respect, Taubes is correct: calorie intake or expenditure, except in the extreme, does not matter as our findings in China confirm.10
WHERE TAUBES GETS IT WRONG
Taubes parts company with the evidence when he gets into the identification of where “bad calories” come from. Taubes sees excess consumption of calorie-contributing carbohydrates (the second of the three competing theories mentioned previously) as the root of all dietary evil. In his view, the consumption of sugar (table sugar or sucrose) and other carbohydrates (i.e., refined carbohydrates, such as starch and fructose) is responsible for the obesity epidemic in the United States and much of the rest of the world. And he blames this spike in carbohydrate consumption on the government’s promotion of the third competing theory: that calories from fat make us fat. In Taubes’ view, the fear of fat engendered by government low-fat policies drove the American public straight into the arms of a high-carb diet because it encouraged the replacement of this fat with carbohydrates. In short, Taubes says that too many carbs is the problem, while the government (or his interpretation of it) says the problem is too much fat.
Taubes argues on historical and scientific grounds that excess fat consumption cannot account for the alarming rise in obesity during the past thirty years the way government pronouncements suggest. Most readers will be familiar with the widespread recommendation to use low-fat foods, as well as the multitudes of “low-fat” food products on the market. Taubes presents a seemingly plausible account of how scientists working in this field got it wrong, partly because they were not very imaginative and partly because they became entrenched in a worldview that discouraged professional challenge against the much-publicized low-fat-focused hypothesis lest they be ridiculed or even risk losing their professional standing. Fat, not carbohydrates, Taubes says, should be our primary source of energy. Fat is good, he says, and not something merely dumped into a body reservoir that eventually becomes adipose tissue.
Before going further, let’s consider what a carbohydrate actually is, especially because Taubes rather arrogantly lambasts scientists for not knowing the properties of this nutrient. (In my experience, it’s really journalists like Taubes, corporate marketing agents, and even some clinicians who are confused about carbohydrates’ definition and meaning.)
The Diversity of Carbohydrates
Carbohydrate is a nutrient found almost exclusively in plants. It is a collection of simple to very complex chemical molecules. Simple carbohydrates include monosaccharides (like glucose, fructose, galactose, mannose, etc.) and disaccharides, which are made up of two chemically bonded monosaccharides (like sucrose [table sugar, made from glucose and fructose] and lactose [milk sugar, made from glucose and galactose]). Linked chains, or polymers, of three or more monosaccharides are called polysaccharides. Glucose (the same molecule as in blood sugar) is the most common monosaccharide unit in polysaccharide chains, with fructose being nearly as common in some foods. Starch, which is the primary polysaccharide in foods like potatoes and cereal grains, is a network of long chains of glucose molecules.
Monosaccharides and disaccharides are often considered “simple” carbohydrates because their molecular size is small, they readily dissolve in water, and they are easily digested and absorbed into the bloodstream. Some people infer that starches are also “simple” because they, too, dissolve in water (though they turn it into a gel or paste) and are readily broken down during digestion into glucose, which is then absorbed into the bloodstream.
Other carbohydrate types are much more complex. Elaborate networks of polymers are formed from chains of monosaccharides, sometimes also including amino acid and fat-like molecular side chains. These polymer networks exhibit a wide variety of chemical, physical, and nutritional properties. A large group of substances generally referred to as the dietary fiber group, for example, are, unlike their simple carbohydrate cousins, generally not digested and absorbed in the gut. Nonetheless, these complex, fiber-like substances still participate in vitally important biological activities: they interact with intestinal microorganisms that break them down into products that benefit the rest of the body, especially the intestines. Indeed, simple and complex carbohydrates, when working together, provide diverse health benefits, including the provision of energy.
Whenever we encounter diversity in nature, we should be slow to dismiss it as unnecessary or unfortunate. A broad spectrum of carbohydrate digestibility and function is very important: it allows the body to adapt to different conditions, ranging from the need for a quick burst of energy to the facilitation of digestion and absorption of other nutrients in the gut.
It’s true that sucrose, the simple disaccharide that comprises table sugar, can be harmful when consumed in isolation. Sucrose is known to have little or no useful health value when extracted from sugar cane and sugar beet plants and added in isolated form to other foods. High-fructose corn syrup is another simple monosaccharide of more recent commercial vintage and exploitation. The latest studies suggest that its effects are as bad as those of sucrose,11 if not worse.12
In order to use this evidence in support of the low-carb movement, Taubes performs a bit of sleight of hand, the crux of which is: refined sugar is bad, therefore all foods that contain sugars (i.e., carbs) are bad. This is poor logic even in the classical sense. We can also highlight the flaws in this reasoning by considering another carbohydrate found in plant food—fiber—and comparing its health effects when in its natural state and when processed, isolated, and consumed as a substance separate from that natural state.
Dietary fiber is extracted from all kinds of whole plants in order to add it to muffins and other baked goods as “bran.” Marketers then claim health benefits from these baked goods, citing the research evidence on the goodness of fiber. But bran doesn’t help us when it’s been extracted from whole plants and then stuck into processed and fragmented foods like breads and breakfast cereals. Although there is some evidence that bran supplements may reduce certain indicators of serious health problems, I find no evidence that, over the long term, this is a good option for actually preventing or treating these problems.13
Whole foods that contain dietary fiber, in its many complex forms, are associated with lower incidence of colon cancer, lower blood cholesterol, and lower breast cancer–inducing estrogen levels. The use of bran isolated from these foods is more about marketing than health. This holds true for many isolated nutrients, which either have no positive health benefits or actually result in damaging effects.
If Taubes and his low-carb compatriots are against ingesting refined (i.e., extracted) sugars, they should say so, and I’d be among the first to support their crusade to eliminate those sugars from our diets. But instead, they tar the entire class of carbohydrates with the same brush, which is an intellectually superficial and dishonest move. (Taubes is more careful than some other low-carb cheerleaders, but not completely so. He should be proactively emphasizing this discrepancy, not allowing it to smolder just below the public