The sugar industry has long defended itself against the notion that sugar is uniquely fattening by repeating the mantra that a calorie is a calorie. The worst that can be said of sugar, the industry argues, is that it tastes good, which leads us to consume too much of it. “There is no difference between the calories that come from sugar or steak or grapefruit or ice cream,” proclaimed industry ads in the 1950s.
That is not actually true, though nutritionists have been slow to come around. Beginning in the 1960s, researchers led by the British nutritionist John Yudkin began to publish the results of experiments in animals and trials in humans suggesting that sugar’s distinctive chemistry had a role in producing an entire cluster of biochemical abnormalities known today as “metabolic syndrome.”
Among these abnormalities is resistance to the hormone insulin, which orchestrates the body’s use of fuels—proteins, carbohydrates and fats, and whether we store them or burn them. That key function apparently goes awry when we consume too much sugar and our cells resist the hormone. Insulin resistance is also the fundamental defect in Type 2 diabetes, the most common form of the disease, and it is common in obesity as well.
The Centers for Disease Control and Prevention estimates that some 75 million Americans now suffer from metabolic syndrome. If sugar consumption is the trigger, as 50 years of research suggests, then it might be as much of a direct cause of diabetes as smoking cigarettes is of lung cancer. Without sugar in our diets, diabetes might be an exceedingly rare disease—as it appears once to have been.