\u201cIt\u2019s viewed as a psychological issue or even a question of character,\u201d says Dr. David Ludwig, who studies and treats obesity at Harvard Medical School.<\/p>\n
The minority position in this field \u2014 one that Dr. Ludwig holds, as do I after years of reporting \u2014 is that obesity is actually a hormonal regulatory disorder, and the hormone that dominates this process is insulin. It directly links what we eat to the accumulation of excess fat and that, in turn, is tied to the foods we crave and the hunger we experience. It\u2019s been known since the 1960s that insulin signals fat cells to accumulate fat, while telling the other cells in our body to burn carbohydrates for fuel. By this thinking these carbohydrates are uniquely fattening.<\/p>\n
Since insulin levels after meals are determined largely by the carbohydrates we eat \u2014 particularly easily digestible grains and starches, known as high glycemic index carbohydrates, as well as sugars like sucrose and high-fructose corn syrup \u2014 diets based on this approach specifically target these carbohydrates. If we don\u2019t want to stay fat or get fatter, we don\u2019t eat them.<\/p>\n
This effect of insulin on fat and carbohydrate metabolism offers an explanation for why these same carbohydrates, as Dr. Ludwig says, are typically the foods we crave most; why a little \u201cslip,\u201d as addiction specialists would call it, could so easily lead to a binge.<\/p>\n
Elevate insulin levels even a little, says Dr. Robert Lustig, a pediatric endocrinologist at the University of California, San Francisco, and the body switches over from burning fat for fuel to burning carbohydrates, by necessity.<\/p>\n
\u201cThe more insulin you release, the more you crave carbs,\u201d he said. \u201cOnce you\u2019re exposed to a little carbohydrate, and you get an insulin rise from it, that forces energy into fat cells and that deprives your other cells of the energy they would otherwise have utilized \u2014 in essence, starvation. So you compensate by getting hungry, particularly for more carbohydrate. High insulin drives carb-craving.\u201d<\/p>\n
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