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I just finished reading Gary Taubes' book, Good Calories, Bad Calories. It's superbly researched and contains crucially important information, but it's a hard read - long, dense, meandering, and repetitive. I fear that many people won't get all the way through it. And while the extensive detail on studies is great, the forest gets a bit lost among all the trees. So here is a summary of the book's main findings, which start with this revolutionary notion:
Overeating is not the cause of obesity, but rather its consequence - a form of body wisdom caused by dietary fuel being abnormally locked away as fat. The cells of your body don't have enough usable energy, so you eat more and move less. Sound crazy? There's actually voluminous research to support this theory.
A Heart-Healthy Diet is High Fat
The book starts with a thorough debunking of the idea that saturated fat and cholesterol cause heart disease. I'm not going to repeat all the evidence here (read the book for that), but there is no question that the dietary cause of atherosclerosis is excessive dietary carbohydrate, not excessive saturated fat. In fact, eating saturated fat is protective of your heart.
Study after study shows this is true. But unfortunately, before the evidence became so clear, the government and medical establishment made some premature pronouncements about low-fat diets being good for your heart, and now they can't find a face-saving way to back off from it.
In addition to the experimental evidence, there is the cultural evidence. The chapter on "Diseases of Civilization" gives example after example of hunter-gatherer cultures that never experienced heart disease, diabetes, obesity, cancer, or the rest of the diseases that plague our society - until they started eating the Western diet dominated by white flour, white sugar, and white rice.
Human breast milk is very high in cholesterol. We evolved as hunter-gatherers eating a high-fat diet composed chiefly of red meat. How in the world could this be bad for us? The new food in our diet - processed and excessive carbohydrate - is the obvious cause of the new diseases. There is a wonderful quote about this from Peter Cleave's testimony before George McGovern's Senate Select Committee on Nutrition and Human Needs:
I don't hold the cholesterol view for a moment. For a modern disease to be related to an old-fashioned food is one of the most ludicrous things I have ever heard in my life. If anybody tells me that eating fat was the cause of coronary disease, I should look at them in amazement. But, when it comes to the dreadful sweet things that are served up … that is a very different proposition.
Low-Fat Diets Make You Fat
The gigantic mistake that the government and medical establishment made in advising a low-fat diet also affected the advice to people struggling with obesity and diabetes. Doctors who recommended a high-fat, low-carb diet for weight loss risked censure because of the widespread - and erroneous - notion that this was bad for the heart.
All obesity research results were interpreted - sometimes tortuously - to be compatible with the idea that carbs are good for you. And one entire area of evidence - the biology of fat metabolism - was completely ignored, because there was no way to reconcile this with the bad advice to eat lots of carbs.
When you eat carbohydrates - particularly processed carbohydrates like white flour, white rice, or sugar - your body secretes insulin to remove the sugar from your blood. Insulin is the hormone necessary to store fat into your fat cells, and also inhibits the release of fat from your fat cells. You can't get fat without insulin, and you can't lose fat with insulin. Obese people virtually always have chronically elevated insulin levels, a precursor to Type 2 diabetes that makes it almost impossible to lose weight.
The only way you can lose weight on a low-fat, high-carb diet is by restricting calories - a semi-starvation diet. Not only is undereating unbearable - for experimental subjects as well as dieters - people almost always regain weight lost from semi-starvation, usually plus some. Study after study shows this to be true, whether you start out fat or lean.
So why isn't everyone fat on a Western diet? People differ in their sensitivity to carbs - they differ in the amount of insulin released after eating carbs, and the sensitivity of their fat tissue to insulin. Some people can eat cake for every meal and not gain weight, but others will quickly fatten on a high carb diet. Unfortunately, people who don't struggle with weight often have little sympathy for those who do because they don't understand that their bodies are different. They think they're morally superior.
Obesity is Not Caused by Gluttony and Sloth
The nice way of saying "gluttony and sloth" is "overeating and lack of exercise". But however you say it, the fact remains: The common wisdom is that fat people cause their own problem by committing two of the seven deadly sins. No wonder there is so much fat bias.
The conventional wisdom is that you get fat if you eat more calories than you expend - the positive caloric balance hypothesis. But the fact that semi-starvation diets almost never produce long-term weight loss strongly suggests that positive caloric balance - overeating and lack of exercise - is not the underlying cause of obesity.
The positive caloric balance hypothesis assumes that (1) the source of the calories doesn't matter - a calorie is a calorie, and (2) energy intake and energy expenditure are independent variables. Neither of these assumptions is true:
- A carb calorie has a very different affect on the body than a fat calorie (see above).
- Energy expenditure is highly dependent on energy intake. Our bodies work hard to maintain a constant body weight. Research shows that if you undereat, your metabolism slows to compensate, and if you overeat, your metabolism speeds up. The idea that you can gain or lose weight over time by altering your intake by 100 calories a day is ridiculous. Your body easily compensates for this small variation (and much larger variations).
Growing children have a positive caloric balance. But the reason they are growing is not because they are eating more calories than they are expending. They are eating more calories than they are expending because they are growing. The cause of their growth is growth hormone, not overeating. The same is true in obesity.
Obesity is a fat storage disorder, not an eating disorder. The body is storing too many of the calories you eat as fat instead of making this dietary energy available to your muscles and organs. On a cellular level, you are experiencing semi-starvation. So you eat more, and you conserve energy by moving less. You don't get fat because you're overeating and under-exercising, you overeat and under-exercise because you're getting fat. Just as vertical growth is driven by hormones, so is the "horizontal growth" of obesity - in this case, insulin. Insulin becomes elevated by a diet too high in carbohydrates.
Have you noticed that people who are fat don't gain weight continuously? You gain weight and then stay at that weight. This is not because of some "set point" that your body is stuck at. Your body maintains a dynamic equilibrium around usable energy, not fat. One hypothesis is that as fat cells expand, it becomes easier for them to release their fat - just as the pressure inside a blown-up balloon will push out the air. Once enough fat is in the cells that it can be mobilized (burned for fuel), a new equilibrium is reached and you stop gaining. Once fat can be mobilized, you don't need to eat as much because your cells have fuel.
The more insulin circulating in your blood, the harder it is to mobilize your fat stores and burn fat for energy. The more carbohydrates you eat, the more insulin will be circulating in your blood. For those who are genetically vulnerable, a high carb diet eventually causes insulin levels to become chronically elevated, while muscle cells become increasingly resistant to insulin (unable to use dietary glucose for energy). Eventually, fat cells also become insulin resistant, and diabetes is the result.
The cellular semi-starvation from excessive fat storage may be why obese women have trouble getting pregnant. It's actually similar to what happens to women who are underweight.
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