Determination of plate waste in primary school lunches by weighing and visual estimation methods: a validation study.

摘要: The aim of this study was to validate the visual estimation method for aggregated plate waste main dish at Portuguese primary school canteens. For purpose lunch measured 505 individual servings, using weighing servings and by a 6-point scale, as developed Comstock et al. (1981). A high variability initial serving weights found with sizes ranging from 88.9 283.3g coefficient variation 5.5% 24.7%. Mean 27.5% according method. There significant bias in conversion estimations actual waste, being overestimated an average 8.0 g (ranging -12.9 41.4 g). According Bland Altman plot, mean difference between methods amplitude interval 102.6g. showed that is not accurate assessing nonselective Our findings are thus very important on considering assessment, since wide introduces relevant when standard portions or random sample servings. Although, greater convenience, time-saving possibility monitor large groups, make assess canteens, these results highlighted need standardization control allow its use.