Junk foods such as sugary sodas and chips make up nearly one-third of calories in the U.S. diet, researchers said.

A study of 4,700 adults showed that, despite the increased popularity of low-carbohydrate diets, soft drinks and pastries pile on more calories in the daily diet than anything else.

“What is really alarming is the major contribution of ‘empty calories’ in the American diet,” said Gladys Block, a professor of epidemiology and public health nutrition at the University of California, Berkeley, who led the study.

Writing in the June issue of the Journal of Food Chemistry and Analysis, Bock and colleagues said that sweets and desserts, soft drinks and alcoholic beverages account for nearly 25 percent of all calories consumed by Americans.

Salty snacks and fruit-flavored drinks add another five percent.

“We know people are eating a lot of junk food, but to have almost one-third of Americans’ calories coming from those categories is a shocker. It’s no wonder there’s an obesity epidemic in this country,” Bock said in a statement.

Bock used data from a U.S. government survey called the National Health and Nutrition Examination Survey. She analyzed the answers of 4,760 adults interviewed in 1999 and 2000.

They were asked to report all the foods they ate in the previous 24 hours.

Sodas contributed 7.1 percent of the total calories eaten. Sweets topped the list, followed by hamburgers, pizza and potato chips.

“It’s important to emphasize that sweets, desserts, snacks and alcohol are contributing calories without providing vitamins and minerals,” said Block.

“In contrast, such healthy foods as vegetables and fruit make up only 10 percent of the caloric intake in the U.S. diet. A large proportion of Americans are undernourished in terms of vitamins and minerals,” Block added.

“You can actually be obese and still be undernourished with regard to important nutrients. We shouldn’t be telling people to eat less - we should be telling people to eat differently.”