Can children and adolescents use photographs of food to estimate portion sizes?

Objective: The goals of this study were to investigate whether children and adolescents can accurately estimate portion sizes of preweighed food by viewing photographs of food, and whether age influences the ability to estimate food portion sizes. Subjects: A total of 63 male and female volunteers aged 9-19 y participated in the study. Design: Each participant received a photographic booklet with photograph series of 13 food items. Participants over 10 y of age were asked to estimate portion sizes of food on 34 plates placed in front of them by comparing the different portions to corresponding photographs of food. Younger participants were asked to estimate portion sizes of food on 17 plates by comparing the portions to photographs. Results: Participants made 2019 comparisons between actual food portion sizes and photographs of food portion sizes. On average, 60% of the comparisons were made correctly. A photograph directly adjacent to the photograph depicting the correct portion size was chosen in 35% of the comparisons and 5% of the comparisons were made incorrectly. Portion sizes were estimated more accurately when the actual served portions of food had exactly the same appearance as the foods portrayed in the photographic booklet. No differences existed between children's and adolescents' abilities to estimate portion sizes using photographs. Conclusions: Large variability may exist in an individual's capability of choosing a photograph that correctly depicts food portion sizes, but the error at the group level is quite small. These data indicate that a photographic booklet of foods can be a useful tool for portion size estimates in these age groups.