Sugar consumption in the U.S. is up 28 percent since 1983. Here are 6 possible reasons why.

1. Fat-free substance. Why such a collective sweet tooth? Blame the burgeoning sales of fat-free foods. Since sugar is fat-free, people think it's okay to eat as much as they want. But fat-free doesn't mean calorie-free, and the resulting weight gain translates into more obesity-related illnesses like diabetes.

2. Portion sizes. With 20-ounce beverages the norm, it's no surprise that 43 percent of our sugar intake comes from drinks. The average American teenager drinks twice as much soda as calcium-rich milk, setting herself up for osteoporosis later on.

3. Poor substitute. Sweetened foods often crowd out more-wholesome choices. USDA data show that people whose diets are high in added sugar eat less protein, fiber, calcium, iron, folate and many other important nutrients.

4. Metabolic mayhem. The body metabolizes all sugars, whether "added" or "naturally occurring," the same. But that's where the similarity ends. Orange juice and a soda may contain the same sugar and calories, Nestle says, but orange juice has vitamins, minerals and phytochemicals you don't get in a soft drink.

5. Keep tabs on intake. The USDA recommends no more than 10 teaspoons (40 grams) of added sugar a day for a 2,000-calorie diet, and six teaspoons (24 grams) for a 1,600-calorie diet. On average, we consume more than twice that much.

6. Read labels. Most sugar we eat is hidden; much of the carbohydrates in many cereals, sports bars and gels are pure sugar. Check the ingredients. All of these terms indicate added sweeteners: sucrose, glucose, dextrose, maltose, fructose, molasses, barley malt, honey, raw, invert or brown sugar, and maple, fruit or corn syrup. Whatever the alias, except for molasses, which has some iron and calcium, they're all nutritional zeroes.