National Geographic : 2013 Aug
• obese? Sugar, we believe, is one of the culprits, if not the major culprit." As far back as 1675, when western Europe was experiencing its rst sugar boom, omas Wil- lis, a physician and founding member of Britain's Royal Society, noted that the urine of people af- icted with diabetes tasted "wonderfully sweet, as if it were imbued with honey or sugar." Two hundred and y years later Haven Emerson at Columbia University pointed out that a remark- able increase in deaths from diabetes between 1900 and 1920 corresponded with an increase in sugar consumption. And in the 1960s the British nutrition expert John Yudkin conducted a series of experiments on animals and people showing that high amounts of sugar in the diet led to high levels of fat and insulin in the blood---risk fac- tors for heart disease and diabetes. But Yudkin's message was drowned out by a chorus of other scientists blaming the rising rates of obesity and heart disease instead on cholesterol caused by too much saturated fat in the diet. As a result, fat makes up a smaller portion of the American diet than it did 20 years ago. Yet the portion of America that is obese has only grown larger. e primary reason, says John- son, along with other experts, is sugar, and in particular fructose. Sucrose, or table sugar, is composed of equal amounts of glucose and fructose, the latter being the kind of sugar you nd naturally in fruit. It's also what gives table sugar its yummy sweetness. (High-fructose corn syrup, or HFCS, is also a mix of fructose and glucose---about 55 percent and 45 percent in so drinks. e impact on health of sucrose and HFCS appears to be similar.) Johnson ex- plained to me that although glucose is metabo- lized by cells all through your body, fructose is processed primarily in the liver. If you eat too much in quickly digested forms like so drinks and candy, your liver breaks down the fructose and produces fats called triglycerides. Some of these fats stay in the liver, which over long exposure can turn fatty and dysfunctional. But a lot of the triglycerides are pushed out into the blood too. Over time, blood pressure goes up, and tissues become progressively more re- sistant to insulin. The pancreas responds by pouring out more insulin, trying to keep things in check. Eventually a condition known as metabolic syndrome kicks in, characterized by obesity, especially around the waist; high blood pressure; and other metabolic changes that, if not checked, can lead to type 2 diabetes, with a heightened danger of heart attack thrown in for good measure. As much as a third of the American adult population could meet the cri- teria for metabolic syndrome set by the National Institutes of Health. Recently the American Heart Association added its voice to the warnings against too much added sugar in the diet. But its rationale is that sugar provides calories with no nutritional ben- e t. According to Johnson and his colleagues, this misses the point. Excessive sugar isn't just empty calories; it's toxic. "It has nothing to do with its calories," says endocrinologist Robert Lustig of the University of California, San Francisco. "Sugar is a poison by itself when consumed at high doses." Johnson summed up the conventional wis- dom this way: Americans are fat because they eat too much and exercise too little. But they eat too much and exercise too little because they're addicted to sugar, which not only makes them fat- ter but, a er the initial sugar rush, also saps their energy, beaching them on the couch. " e rea- son you're watching TV is not because TV is so good," he said, "but because you have no energy to exercise, because you're eating too much sugar." The solution? Stop eating so much sugar. When people cut back, many of the ill e ects disappear. e trouble is, in today's world it's extremely di cult to avoid sugar, which is one reason for the spike in consumption. Manufac- turers use sugar to replace taste in foods bled of fat so that they seem more healthful, such as fat-free baked goods, which o en contain large quantities of added sugar. It's a worst-case scenario: You sicken unto "WE HAVE A BIG PROBLEM. Our world is flooded with Rich Cohen's ninth book, on the 1985 Chicago Bears, will appear in October. Robert Clark's story on the Denisovans was published last month.