WASHINGTON – More than 40% of American households’ total food budget is spent on foods prepared outside of the home, up from 25% in 1970. Because this marked increase occurred as obesity rates were trending upward, researchers and policymakers theorize dining out amounts to excessive caloric intake and poor diet quality, according to the U.S. Department of Agriculture's Economic Research Service (E.R.S.).

E.R.S. researchers recently took two days of adults’ dietary intake data from two national surveys to estimate how changes in the number of meals consumed away from home in a day change the total number of calories consumed and various measures of daily diet quality. Food away from home has a significant impact on caloric intake and diet quality, they discovered. Each additional meal or snack eaten away from home adds an average of 134 calories that day, compared with the same meals or snacks prepared at home.

According to the agency, eating lunch away from home has the biggest impact on the average adult – adding 158 calories to daily intake, compared with lunch prepared at home. Eating dinner out increases intake by 144 calories. Each away-from-home snack adds a little more than 100 calories to daily intake, compared with snacks prepared at home. Breakfast away from home adds 74 calories.

Eating out increases the percent of daily calories from fat and added sugar. This indicates that individuals do not compensate for the less healthful food-away-from-home meals with more healthful foods at other meals in the day,

Daily caloric intake from food prepared away from home also depends on an individual’s weight. An away-from-home meal adds an average of 239 calories to daily caloric intake for obese individuals (Body Mass Index greater than or equal to 30) versus 88 additional calories for those with a B.M.I. less than 25.