People are good at estimating how much they spend on food, both in restaurants and at home.  The Seattle Obesity Study, based on 447 households, compared self-reported food expenditures with actual food store and restaurant receipts collected over a period of two weeks. Being able to estimate food expenditures opens the door to new studies in nutrition economics on whether eating healthy adds to consumer food costs.

Participants were adult men and women who were the primary food shoppers for the household. They were asked to estimate how much money the household spent per week at supermarkets or grocery stores, and how much on eating out, including at cafeterias, vending machines, and schools. They were also asked to keep all food expense receipts for groceries and eating out for the entire household for a period of two weeks.

Based on household receipts, the average per person food expenditures at grocery stores was $96, as compared to $90 estimated by self-reporting. The corresponding per person amounts for eating out were $45 from receipts and $43 from self-reports. As expected, higher education and higher income were each associated with higher per person spending at food stores and on eating out. Higher-income households were also more likely to underestimate what they spent on food when compared to actual receipts.

The study represents the first validation of food expenditure questions included in the National Health and Nutrition Examination Survey (NHANES), an ongoing federal study on diets and health. NHANES findings are used drive and inform public health nutrition policy and programs.

The study was conducted by the Center for Public Health Nutrition in the School of Public Health and the Urban Form Lab at the University of Washington.

The study was just published in the European Journal of Clinical Nutrition. Researchers included Anju Aggarwal, Colin Rehm, Anne Vernez Moudon, and Adam Drewnowski.