Estimation of sex- and age-specific food portion sizes among Japanese children and adolescents aged 3–17 years

To provide a scientific basis for establishing a portion size database for dietary assessment and nutritional education, we determined the portion sizes of commonly consumed food groups among Japanese children and adolescents aged 3-17 years. This study analysed 8-day weighed dietary record data from a nationwide survey conducted between November 2016 and August 2020. Participants were grouped into preschoolers (3-6 years, n=572), elementary school children (7-12 years, n=406) and middle/high school students (13-17 years, n=379). Age- and sex-specific portion sizes of 73 food groups were calculated as weighted averages of median portion sizes of the food items within each group, using the number of consumers for each item as weights. Overall, older participants had larger portion sizes than younger participants, but the magnitude of this difference varied between sexes and food groups. For most food groups, middle/high school students consumed 1.2-1.5 times (29 and 45 food groups for boys and girls, respectively) or 1.6-1.9 times (32 and 18 food groups for boys and girls, respectively) larger portion sizes than preschoolers. Portion sizes among middle/high school students were at least twice as large as those among preschoolers for ten food groups in boys, including staple foods, pork/beef, some vegetables, some beverages and salty snacks, but only for three food groups in girls. In conclusion, these differences in portion sizes according to age, sex and food group should be taken into account when assessing dietary intake and designing nutritional education for portion size control.