© Goran Bogicevic -

Fast-food restaurants take a lot of blame for the U.S. obesity epidemic but a new study weighs in with the news that eating out -- period -- piles on the calories, sugar, saturated fat and sodium.

The study, appearing online in Public Health Nutrition, finds that on days when adults ate at a restaurant -- fast-food or full-service -- they consumed about 200 additional total daily calories.

"The United States is one of the most obese nations in the world, with more than one in three adult men and women in defined as obese," said Dr. Binh Nguyen of the American Cancer Society. "Just as obesity rates rise, there's been a marked increase in total energy consumption consumed away from home, with about one in four calories coming from fast food or full service restaurants in 2007. Our study confirms that adults' fast-food and full-service restaurant consumption was associated with higher daily total energy intake and poorer dietary indicators."

For the current study, Nguyen and Lisa M. Powell of the University of Illinois at Chicago used recent data from more than 12,000 respondents between the ages of 20 and 64 taking part in the National Health and Nutrition Examination Survey 2003 (NHANES). Participants were asked about visits to fast-food and full-service restaurants on two successive days.

The study found on days when eating at a fast-food restaurant, there was a net increase of total energy intake (194.49 kcal), saturated fat (3.48 g), sugar (3.95 g) and sodium (296.38 mg). Eating at a full-service restaurant was also associated with an energy intake (205.21 kcal), and with higher intake of saturated fat (2.52 g) and sodium (451.06 mg).

Individual characteristics moderated the impact of restaurant food consumption. Net energy intake was larger for black adults compared with their white and Hispanic counterparts and greater for middle-income v. high-income adults.

The researchers say the larger adverse effect they measured on energy intake for some lower socio-economic and minority populations has policy implications. They say efforts to improve diet and reduce energy intake from restaurant sources could actually help to reduce racial and socio-economic disparities in Americans' diets.

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