A 5-Min Extension of Eating Time during School Lunches Was Associated with Reduced Plate Waste among Japanese Junior High School Students

Substantial plate waste in Japan reduces dietary intake and sustainability. Although longer eating times reportedly reduce plate waste in other countries, evidence from Asia remains limited. We examined whether extending eating time from 15 to 20 min reduces plate waste and improves perceived adequacy of lunchtime among junior high school students. This study employed a before–after comparison design without a control group and was conducted in a Japanese public junior high school. The same lunch menu was served on two Fridays under 15- and 20-min lunch conditions. Of 144 second-grade students, 112 who completed both conditions were analyzed. Individual-level plate waste of rice, milk, simmered mackerel, cabbage salad, and Japanese rice flour dumpling soup (dango-jiru) was weighed. Students completed questionnaires assessing perceived adequacy of lunchtime, physical condition, and hunger. In the total sample, a decrease was observed in plate waste for rice (p=0.041) and dango-jiru (p=0.030) as well as total plate waste per student (p=0.019). Among girls, reductions were observed for dango-jiru (p=0.006) and total plate waste (p=0.003); no significant changes were found among boys. The proportion of students reporting lunchtime as “sufficient” increased from 70.0% to 88.2% (p<0.001). Physical condition and pre-lunch hunger did not differ between conditions. Extending eating time by 5 min reduced plate waste for selected meal components and improved students’ perceived adequacy of lunchtime, with stronger effects among girls. Securing approximately 20 min of seated eating time during school lunches may represent a simple, low-cost strategy to support school nutrition and reduce food loss.