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The Diets That Work

You wouldn't know it from reading the latest dietary headlines, but all of the popular diets—from Atkins to Dean Ornish (Bill Clinton's weight-loss plan) to the diet-of-the-moment, Paleo—are successful because the most important change they advise is the same: stop eating refined carbohydrates. This only reminds us of what had been the conventional wisdom in medicine for hundreds of years before the USDA stepped in: that sugar, flour, potatoes, and rice are what make a person fat, not meat and milk.

Forty years into the low-fat, high-carbohydrate way of eating—we can thank it for "diabesity," shorthand for the societal prevalence of type II diabetes paired with obesity—it seems clearer than ever that our problem lies not simply in carbohydrates, but in their fundamental addictiveness. They sidestep our defenses against overeating, activate brain pathways for pleasure, and make us simultaneously fat and malnourished. They keep us coming back for more, even as they induce physical decline and social rejection. They achieve this more effectively than the controlled substances that can get a guy thrown into jail. Maybe the question isn't whether carbohydrates are addictive, but whether they are the most addictive substance of all.

In 2007, researchers at the University of Bordeaux, France, reported that when rats were allowed to choose between a calorie-free sweetener and intravenous cocaine, 94 percent preferred the sugar substitute. The researchers concluded that "intense sweetness can surpass cocaine reward. . . . The supranormal stimulation of these receptors by sugar-rich diets, such as those now widely available in modern societies, would generate a supranormal reward signal in the brain, with the potential to override self-control mechanisms and thus to lead to addiction." Nicole Avena, an expert in behavioral neuroscience at the University of Florida in Gainesville, has spent many hours analyzing the behavior of rats enticed into sucking up sugar. She says that feeding on sugar can, like snorting coke, lead to bingeing, withdrawal, and craving. It does this by lighting up the same circuitry within the brain triggered by cocaine and amphetamines, the dopamine center.

But a carbohydrate addiction is potentially more destructive than an 8-ball-a-day habit, because it hijacks your metabolism. If you eat a low-carb diet, you are able to remain satiated between meals, because the body will burn its fat stores. But eating carbs, especially refined varieties like sugar or flour, sweetened drinks, or starches, causes the body to release the hormone insulin. The body secretes insulin as a response to high blood sugar—a serious, even potentially lethal health risk over time. The hormone directs cells to extract sugar from the blood and store it as fat, and what's worse, in order to get sugar out of the blood as efficiently as possible, insulin makes it extremely difficult for the body to burn its fat stores. Over time, the presence of insulin in our carb-heavy diet causes diminishing returns. As our cells become resistant to the effects of insulin, our bodies frequently release even more of it to compensate. The result is a blood-sugar vacuum: The body craves more of what the hormone feeds on and triggers our hunger mechanism, which works subconsciously, to direct us toward the nutrient causing all the problems in the first place—carbohydrates. You get fatter and your body craves even more carbs in order to maintain your increasing weight. Drug cartels can only dream of a narcotic with an addiction cycle this powerful.

Once hooked, can you quit your carb addiction? It's not like there's a carb-cessation program at Promises, after all. Taubes says it won't be easy, but given the alternatives, you simply have to try. And cold turkey is as good a method as any. "Anecdotal evidence suggests that the craving for carbs will go away after a while," he says, "although whether a while is a few weeks or a few years is hard to say." And frighteningly like an addict in recovery, you're unlikely ever to be totally cured, and you'll always be tempted to relapse when the opportunity arises. Be warned: The number of Panera Bread outlets is 1,421 and counting.

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How You Get Hooked (Over Time)

1. When you take in carbs, like Gatorade or whole-wheat bread, you secrete the hormone insulin. Even thinking about carbs causes this to happen.

2. Refined carbs spike blood sugar, and this is a big problem. The first result is that your body immediately stops burning its existing fat stores.

3. Too much blood sugar is a dangerous situation, and in response, insulin, a hormone, rips it from your blood and tells the body to store the energy as fat (in men this first happens around the waist).