Nearly one-third of the calories in the U.S. diet come from junk food, researcher finds

Gladys Block, professor of epidemiology and public health nutrition at the University of California, Berkeley, has quantified the types of foods the United States population eats and ranked them by the amount of calories they contribute.

Her findings, published in the June issue of the Journal of Food Chemistry and Analysis, reveal that three food groups -- sweets and desserts, soft drinks and alcoholic beverages -- comprise almost 25 percent of all calories consumed by Americans. Salty snacks and fruit-flavored drinks make up another five percent, bringing the total energy contributed by nutrient-poor foods to at least 30 percent of the total calorie intake.

"What is really alarming is the major contribution of 'empty calories' in the American diet," said Block. "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."

For her analysis, Block used data from 4,760 adults who took part from 1999 to 2000 in the National Health and Nutrition Examination Survey (NHANES). Participants in the survey were asked to report all the foods they ate in the prior 24 hours. For comparison, Block also analyzed NHANES III data collected between 1988 and 1994.

Block categorized food codes from both of the NHANES surveys into 144 total food items. She then categorized those items into 23 food groups.

Among the food items, soft drinks and pastries led the list of top 10 foods contributing the most calories to the American diet. As the leader of the pack, sodas alone contributed 7.1 percent of the total calories in the U.S. population. Foods such as hamburgers, pizza and potato chips rounded out the top five food items.

When comparing the rankings from the NHANES III survey with the 1999-2000 data, Block did not find major changes. Under the food group category, bread, rolls and crackers contributed 10.7 percent of calories in the earlier survey but only 8.7 percent in the later one. Soft drink consumption was up slightly, from 6 percent of calories in 1988-1994 to 7.1 percent in 1999-2000.

Block's calculations took into account the number of respondents who reported eating a particular food item, the portion sizes of the food, and the nutrient and energy content of the food. For example, the calories provided by sodas were summed up from individual reports and then divided by the total number of calories consumed by the entire population to get the proportion of energy provided. The foods then were ranked by their contribution to the total energy intake.

"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. 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."

Block also published a recent analysis of physical activity among the U.S. population that found that Americans are primarily sedentary. "The combination of our sedentary lifestyle with our poor eating habits goes a long way to explain the current rise of overweight and obese Americans," said Block.