Research Article: Effects of a nutritional intervention using pictorial representations for promoting knowledge and practices of healthy eating among Brazilian adolescents

Date Published: March 11, 2019

Publisher: Public Library of Science

Author(s): Laís Gomes Fonseca, Maria Natacha Toral Bertolin, Muriel Bauermann Gubert, Eduardo Freitas da Silva, Jimmy Louie.


This study aimed to evaluate the effect of a nutritional intervention involving a problem-raising approach and the use of pictorial representations on the promotion of knowledge and practices of healthy eating among adolescents. This randomized study included 461 adolescents from public schools in Brasilia, Federal District, Brazil (intervention group: 273 students from four schools; control group: 188 students from three schools). Mean age was 14.8±1.0, and 52.9% were boys. The intervention consisted of three meetings with interactive activities about principles of healthy eating, food classification, importance of reading labels and analyzing food advertising critically, and representations of healthy and unhealthy meals and their sugar, salt, and fat content. Pictorial materials consisted of food drawings, food models, and a food packaging model. Controls were not exposed to any activity. Dietary knowledge, consumption, and behaviors were the variables of interest. The intervention group showed a higher mean score of correct answers to questions about dietary knowledge than the control group (p = 0.0006), with higher odds of correctly answering questions about in natura (OR: 3.7; 95% CI: 1.9–6.6), minimally processed (OR: 3.6; 95% CI: 1.9–6.4), processed (OR: 2.2; 95% CI: 1.1–4.3), and ultra-processed foods (OR: 3.5; 95% CI: 1.8–6.6) and composition of ultra-processed foods (OR: 2.4; 95% CI: 1.3–4.4). Participants in the intervention group were also 2.5 times more likely to correctly answer questions about the importance of the dietary environment (95% CI: 1.1–5.5) and caution with food advertising (95% CI: 1.2–5.3) than controls. Increased weekly consumption of vegetables (p = 0.0077; OR: 2.4; 95% CI: 1.26–4.51) and reduced consumption of soft drinks (p = 0.0212; OR: 0.36; 95% CI: 0.15–0.86) were observed in the intervention group compared to the control group. The proposed intervention increased adolescents’ knowledge and improved some of their dietary habits. Educational activities using a problem-raising approach and pictorial representations of food appear to be effective in promoting healthy eating practices among adolescents.

Partial Text

The health status of Brazilian adolescents has changed significantly in recent years, with an increasing prevalence of obesity and other comorbidities, such as hypertension and hypercholesterolemia, which were once limited to adults [1–2]. A major factor contributing to this shift is the decline in the quality of the diet of adolescents [2]. Results of national surveys show increased consumption of ultra-processed and processed foods as well as reduced intake of in natura and minimally processed foods among adolescents [3].

This was an experimental, randomized, controlled nutritional intervention study. Written informed consent was obtained from all parents or legal guardians authorizing their children to participate in the study. All students who agreed to participate signed an assent form before inclusion in the study. The study was approved by the Research Ethics Committee of the School of Health Sciences at University of Brasilia in Brazil (approval no. 55653516.6.0000.0030).

The initial sample consisted of 676 adolescents, and 31.8% were lost before the end of the study. Losses were mainly due to the absence of students on the second occasion of questionnaire administration. Only those who completed the questionnaire in both occasions (pre- and post-intervention) were included in the analyses, resulting in a final sample of 461 adolescents. Of these, 273 students were in the intervention group and 188 in the control group. The mean age of participants was 14.8 ± 1.0 years, and 52.9% were boys, with no significant difference between groups.

This study showed that a short-term nutritional intervention based on an active, participatory, problem-raising approach with the use of pictorial representations of food was able to increase dietary knowledge among adolescents. The intervention also had some influence on their dietary consumption, leading to increased vegetable consumption and reduced soft drink intake.




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