To validate a picture book for estimation of food portion sizes using two approaches: (i) 'perception' of food portions by comparison with a series of food photos; and (ii) 'conceptualization and memory', using the same photos to estimate the amount of served food one hour after self-served food portions.
Each partner developed a country-specific picture book based on the so-called EPIC-Soft picture book. Representative and common photo series were chosen achieving approximately 25 % of the original picture book (n 23). Three portions from each photo series were randomly selected.
The study was performed within the Pilot study in the view of a Pan-European dietary survey - Adolescents, adults and elderly (PILOT-PANEU) project.
A sample of adolescents and adults was recruited in five countries: Bulgaria (n 103), Finland (n 34), Germany (n 69), Hungary (n 62) and Portugal (n 77).
Among the portions of the corresponding photo series and depending on the type of food, from 18 % (cheese) to 96 % (ratatouille) of participants chose the correct portions. In the perception study, agreement between the portions shown and reported was substantial (intraclass correlation coefficient (ICC)=0·805) and the mean difference was very low. In the memory study, agreement between the served and reported portions was lower than in the perception study (ICC=0·536). Agreement also seemed to decrease as the appearance of food on the plate differed from food in the picture.
Overall, the picture series selected can be applied in future intake surveys to quantify foods similar to those depicted in the pictures.