Food photographs in portion size estimation among adolescent Mozambican girls

Objective To assess the validity of food photographs in portion size estimation among adolescent girls in Mozambique. The study was carried out in preparation for the larger ZANE study, which used the 24 h dietary recall method. Design Life-sized photographs of three portion sizes of two staple foods and three sauces were produced. Participants ate weighed portions of one staple food and one sauce. After the meal, they were asked to estimate the amount of food with the aid of the food photographs. Setting Zambezia Province, Mozambique. Subjects Ninety-nine girls aged 13-18 years. Results The mean differences between estimated and actual portion sizes relative to the actual portion size ranged from -19 % to 8 % for different foods. The respective mean difference for all foods combined was -5 % (95 % CI -12, 2 %). Especially larger portions of the staple foods were often underestimated. For the staple foods, between 62 % and 64 % of the participants were classified into the same thirds of the distribution of estimated and actual food consumption and for sauces, the percentages ranged from 38 % to 63 %. Bland-Altman plots showed wide limits of agreement. Conclusions Using life-sized food photographs among adolescent Mozambican girls resulted in a rather large variation in the accuracy of individuals' estimates. The ability to rank individuals according to their consumption was, however, satisfactory for most foods. There seems to be a need to further develop and test food photographs used in different populations in Sub-Saharan Africa to improve the accuracy of portion size estimates.