The American Diet Then and Now: How Snacking Is Expanding the Country's Waistline Americans consume 570 calories more per day than they did in the 1970s.

June 28, 2011 -- Americans eat roughly 570 calories more per day than they did in the 1970s, according to a new study. While supersize portions are partly to blame, steady snacking is the bigger culprit.

"We're a generation of constant eaters," said Barry Popkin, distinguished professor of nutrition at the University of North Carolina at Chapel Hill. Popkin used surveys to probe the American diet since 1977. Americans began eating more in the '80s and '90s, but in recent years, they've begun eating and drinking more often -- like almost all the time.

"It used to be you'd have three meals a day. And if you snacked, it was unsweetened tea or coffee," said Popkin. "Nowadays, everywhere you turn there's food. If you're driving, you have a big bag of Doritos next to you while you drive."

More than one-quarter of adults in the United States are obese, according to a 2010 report from the Centers for Disease Control and Prevention -- a proportion that has steadily grown over the past 30 years as Americans tend to "eat more and do less," said Dr. David Katz, director of the Yale University Prevention Research Center.

"We joke about the 'see food' diet. We see food and we eat it," said Katz, explaining how Americans have come to expect food at every turn. "People panic at the thought of spending a couple of hours somewhere where there might not be refreshments on hand."

Despite their growing obsession with food, fewer Americans are willing to sit down and enjoy it.

"We're no longer eating at a table with a knife and fork," said Keith Ayoob, director of the Rose R. Kennedy Center Nutrition Clinic at Albert Einstein College in New York City. "As a society, we think it takes too long to eat a bowl of cereal. We want a breakfast you can hold in one hand."

As a result, Americans choose foods that are loaded with flavor and calories for immediate gratification, only to feel hungry again an hour or two later.

But it's not just salty foods that are expanding the nation's waistline. Sugary drinks like soda, fruit juice and sweetened coffees pack on the pounds too.

"We're drinking ourselves to death," Popkin said. "Several hundred of these extra calories are coming just from drinks."

Popkin said he hopes the study will be an eye-opener for people who might not realize how many calories they're consuming.

"We have to focus a lot more attention on cutting down how often we eat if we're truly going to do something about this as a society," he said. But in a world where people are perpetually bombarded by food and drink advertising, it won't be easy.

"We don't need to have food every couple hours, so we need to change the environment so that we don't encounter food everywhere we go," said Katz, adding that a little willpower can go a long way.

"We kind of just have to grow up," he said. "We weigh too much and our health is on the line."