In this series, we will look at the basics of metabolism and discuss the very well-known science around obesity. Many of the diseases that bedevil humanity flow from obesity, including cancer and Type 2 diabetes, and so understanding metabolism and the causes of obesity is ground zero in the fight for a long life and good health.

It would be hard to overstate the level of excellence and detail in Good Calories, Bad Calories by Gary Taubes. The level of detail is unsurpassed and his observations about things that are, if properly thought through, so obviously true that makes such observations highly memorable. Why, for example, are there no obese animals?

On the highest level, Taubes set out to disprove the energy balance equation or hypothesis, which was the idea that obesity is caused by overeating. Overeating, in this instance, is defined as eating more calories than the body can use. Under this theory, any excess calories are stored as fat. The body, it is asserted, stores or uses calories like your car uses gas. This theory is predicated on the belief that all calories are fundamentally the same and that the body burns them universally the same way for the same reasons at the same rate.

Further, if one accepts that this is true, then those that eat too many calories and become obese are morally inferior beings because they can’t control their appetite. Overeating is purely gluttony, a deadly sin. As such, it is perfectly acceptable to hold them up for social ridicule. At least in the United States, it is socially acceptable to mock and ridicule fat people in the most personal of terms. Entire comedic careers are based on mocking fat people.

All well and good, accept for the part where the energy balance hypothesis is pernicious nonsense. Calories, to begin with, are a human concept that the body knows nothing of, and the human body is far better engineered than the gas tank on a car. Human biology is a marvel of adaptation that doesn’t predicate its survival on anything as delicate as appetite discipline as Taubes painstakingly points out. There are so many aspects to human metabolism that it takes many books to describe it in detail, yet all discussions of metabolism must cover the role of insulin in order to be even a bit complete.

Insulin is a hormone produced in the pancreas. The Wikipedia entry for insulin is very complete and worth quoting here at length:

Insulin (from Latin insula, ‘island’) is a peptide hormone produced by beta cells of the pancreatic islets; it is considered to be the main anabolic hormone of the body. It regulates the metabolism of carbohydrates, fats and protein by promoting the absorption of glucose from the blood into liver, fat and skeletal muscle cells. In these tissues the absorbed glucose is converted into either glycogen via glycogenesis or fats (triglycerides) via lipogenisus or, in the case of the liver, into both. Glucose production and secretion by the liver is strongly inhibited by high concentrations of insulin in the blood. Circulating insulin also affects the synthesis of proteins in a wide variety of tissues. It is therefore an anabolic hormone, promoting the conversion of small molecules in the blood into large molecules inside the cells. Low insulin levels in the blood have the opposite effect by promoting widespread catabolism, especially of reserve body fat.

One could read that definition over and over and come to a far greater understanding of obesity as well as the function of diabetes. There is more to be learned here than every word of ad copy produced by ‘Weight Watchers’ or any organization that promotes the energy balance hypothesis.

Just taking the last sentence: “Low insulin levels in the blood have the opposite effect by promoting widespread catabolism, especially of reserve body fat.” This illustrates a core point: the presence of insulin stops the mobilization of body fat for energy. If there is insulin in the bloodstream, body fat will not be turned into energy because the body has energy floating around in circulation already.

That leaves only this salient question: what causes the pancreas to secret insulin? The answer is carbohydrates. Ingestion of carbohydrates triggers the secretion of insulin, and highly refined, easy to digest carbohydrates, like a cupcake, causes a massive release of insulin because of the artificially high amount of sugar in such foods. Nature would not create such a confection. Conversely, when insulin levels are low, the body is engaged in mobilizing fat to generate energy. Note the lack of mention about calories. From a fat gaining perspective, calories aren’t the issue; insulin is. Accepting this is a good first step in understanding how to manage this marvelous evolutionary machine we’ve inherited.

Gary Taubes is interviewed by the fine people at the Institute for Human and Machine Cognition:

Listen here as Ricky Gervais justifies mocking fat people DIRECTLY by quoting the calorie theory of obesity: