‘Energy intakes of US children and adults by food purchase location and by specific food source’ published in Nutrition Journal , is “the first-ever study of dietary energy intakes by age group, food purchase location and by specific food source”, claim its authors: Dr Adam Drewnowski and Dr Colin D Rehm from the University of Washington, Seattle.

As all foods consumed by participants in the government-run National Health and Nutrition Examination Surveys (NHANES) are now color coded by location of purchase (eg. store, quick-service restaurant/pizza (QSR), full-service restaurant (FSR), school/workplace cafe, vending machine etc), it is possible to determine much more accurately where our calories are coming from, they explain.

Contrary to popular belief, restaurant-sourced pizza, burgers, chicken and French fries accounted for less energy than store-sourced breads, grain-based desserts, pasta and soft drinks

And while “individuals tend to under-report the consumption of foods perceived to be less healthful [such as those consumed at fast-food chains]”, the findings might surprise many people, they add.

Overall, analysis of three sets of NHANES data (2003/4, 2005/6 and 2007/8) shows that 63-76% of calories in the US diet depending on age group are from products brought at stores, while quick- and full-service restaurants contribute 17-26% of calories. The rest come from multiple sources including vending machines and school and work cafeterias.