OBJECTIVES: Weighing individual plate waste provides reliable estimates of food intake by physically weighing individual food components to the nearest gram before and after a meal. Weighing aggregate, school-level food waste may be an inexpensive and less time-consuming alternative. However, it has not been determined whether aggregate plate waste is an accurate measure of individual plate waste. This pilot study therefore aimed to evaluate the accuracy of aggregate plate waste for quantifying food waste in a school cafeteria setting in comparison to individual weighed plate waste.
METHODS: This study took place in an urban, low-income school district in Massachusetts. Four elementary schools that shared two identical cafeterias and served the same foods each day participated in the study. Participating students in the four schools had similar demographic characteristics. Cafeterias were randomly assigned to either individual or aggregate plate waste measurements. Plate waste was collected for 4 days from approximately n = 850 students in each cafeteria on the same days. For individual plate waste, the % consumed was calculated for each food item on each student's tray. In the cafeteria with aggregate-level measurements, waste was separated by component (entrée, vegetable, fruit, and milk), and weighed to calculate the % consumed. Intraclass correlation coefficients (ICCs) were calculated to assess the agreement between aggregate plate waste and individual-level plate waste.
RESULTS: Agreement was excellent for entrées (ICC = 0.90) and vegetables (ICC = 0.78), but poor for milk (ICC = 0.22) and fruits (ICC = 0.23). The overall agreement for all four components combined was excellent (ICC = 0.75).
CONCLUSIONS: Results suggest that aggregate plate waste may be a reasonable measure of individually weighed plate waste, but additional research is warranted.
