Assessing food choice in school children: reliability and construct validity of a method stacking food photographs

A method utilizing pictures was used to assess food choice with 44 school boys in three different age groups (10, 13 and 16 years old). The aim of the study was to test reliability and construct validity (i.e. inter-instrument agreement) of food choice assessed when the boys were asked to compose breakfasts. The focus was on choices of milk, margarine, bread and breakfast cereals, as in these food groups it is possible to choose between low-fat/high-fat and low-fibre/high-fibre products. Subjects were asked to repeat their composing of breakfasts after eight weeks, and to complete a four-day food record on breakfasts after the second interview occasion. For comparisons between food choices a new non-parametric statistical method was used. Both reliability and construct validity were good for choices of milk and margarine. The unreliability could be explained as random in nature or in terms of healthier choices in the second interview.