Good Calories, Bad Calories: What Really Makes Us Fat?
(Page 3 of 6)
October/November 2008
By Gary Taubes
The third fact that was regrettably neglected during the years that we came to believe in the evils of saturated fat was that back in the 1950s and early 1960s, biochemists and physiologists had already figured out what it is that regulates the accumulation of fat in our fat tissue. In other words, scientists have known what makes us fat for almost half a century.
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The Skinny on Fat
As it turns out, every hormone in our body works to release fat from our fat tissue, with the singular exception of insulin, which works to put it there. And insulin levels in our blood are determined primarily by the carbohydrate content of our diet. The more carbohydrates we consume, and the easier they are to digest, the higher our insulin. Insulin tells our fat tissue to accumulate fat. So long as insulin levels remain elevated, fat is locked in the fat tissue and can’t escape.
What’s even more remarkable — and completely ignored in all discussions of obesity and weight since the 1970s — is that we must eat carbohydrates to accumulate excess fat in our fat tissue. It’s only by eating carbohydrates that we can obtain alpha glycerol phosphate, an enzyme that is an absolute requirement for storing fat. This enzyme fixes the fat in the fat tissue in a way that it can’t slip back out through the fat cell membranes and escape into the blood stream. This is why the more carbohydrates we consume, the more fat we will store. The less carbohydrates, the less fat.
After a meal is digested, insulin levels should decline. When this happens, fat is released from the fat tissue in the form of fatty acids and these are then burned in cells for fuel. For this reason, another necessary requirement for remaining lean is to have lengthy periods during which insulin levels are low and we burn our fat for fuel. When insulin levels remain elevated, fat can’t escape from the fat tissue. It goes in, but it doesn’t come out, and we can’t use it for energy. A meal without carbohydrates is a meal that doesn’t stimulate any significant insulin secretion. You store very few, if any, calories as fat, and you get plenty of opportunity to burn the fat you had stored.
The reason this science was left behind was a simple one. Diet doctors in the 1960s read the same medical literature that I did decades later, and they then began prescribing carbohydrate-restricted, mostly meat diets to their patients. But a low-carbohydrate diet is high in fat, and fat was thought to be a killer. Indeed, in 1965, the same year that the American Physiology Society published an 800-page Handbook of Physiology describing the recent research in the regulation of fat tissue, the research that implicated carbohydrates and insulin in fat storage, the Harvard nutritionist Jean Mayer was quoted in The New York Times saying it would be the equivalent of “mass murder” to prescribe low-carbohydrate diets to treat obesity. Mayer’s reasoning was that these diets were high in fat and the fat would cause heart disease. That’s how the medical establishment has treated it ever since, even after researchers revealed that high fat diets actually improve cholesterol profiles, rather than worsen them.
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