“Snacking may be an important source of nutrients that we would like to increase in our diet,” Mattes said. But when snacks become a source of excess calories, they contribute to obesity, he said.
Further, Americans are now more likely to slurp up calories in the form of sugary drinks. The percentage of Americans who consume calorie-rich beverages on a daily basis increased from 41 percent in 1965 to 67 percent in 2004, according to a 2009 study Mattes published in the American Journal of Clinical Nutrition. Beverages can account for up to half the calories Americans ingest outside of mealtimes, he said.