Abstract

This study aimed at assessing the association between psychosocial aspects and fruit and vegetable consumption in adolescents. Cross-sectional study developed with 327 adolescents from a public school in Brazil. A questionnaire developed for adolescents was applied to assess the influence of self-efficacy, family, peers, and body image on the consumption of fruits and vegetables. Specific questions assessed the intake frequency of fruits and vegetables, and the mean consumption was estimated using two 24-hour recalls. Scores related to psychosocial aspects were described as mean and median and the weight status was classified based on the body mass index. The average daily consumption of fruits and vegetables was 36.2 g and 45.4 g, respectively. Self-efficacy and the influence of peers were associated with an increase in the amount and frequency of fruits and vegetables consumption. Adolescents with higher scores of self-efficacy had greater average consumption of fruits and vegetables when compared to those with lower scores. The same was observed for the influence of peers. Self-efficacy and the influence of peers were the factors that most influenced the consumption of fruits and vegetables in adolescents.

Key words:
Psychosocial aspects; Adolescents; Fruits; Vegetables; Questionnaire

Resumo

O objetivo do estudo foi avaliar a associação entre aspectos psicossociais e o consumo de frutas e hortaliças em adolescentes. Estudo transversal desenvolvido com 327 adolescentes de uma escola pública do Brasil. Um questionário desenvolvido para adolescentes foi aplicado para avaliar a influência da autoeficácia, família, pares e imagem corporal sobre o consumo de frutas e hortaliças. Questões específicas avaliaram a frequência de ingestão de frutas e hortaliças e o consumo foi estimado por meio de dois recordatórios de 24 horas. Os escores relacionados aos aspectos psicossociais foram descritos por média e mediana e a condição de peso foi classificada com base no índice de massa corporal. O consumo diário médio de frutas e hortaliças foi de 36,2 g e 45,4 g, respectivamente. A autoeficácia e a influência dos pares associaram-se ao aumento da quantidade e da frequência de consumo de frutas e hortaliças. Os adolescentes com maiores valores no escore para autoeficácia apresentaram maior média de consumo de frutas e hortaliças quando comparados àqueles com menores escores. O mesmo foi observado para a influência dos pares. A autoeficácia e a influência dos pares foram os fatores que mais influenciaram o consumo de frutas e hortaliças em adolescentes.

Palavras-chave:
Aspectos psicossociais; Adolescentes; Frutas; Hortaliças; Questionário

Introduction

Fruit and vegetable consumption is widely recommended for their health protection properties, being associated with a reduced risk of developing cancer, cardiovascular diseases¹1 Aune D, Giovannucci E, Boffetta P, Fadnes LT, Keum N, Norat T, Greenwood DC, Riboli E, Vatten LJ, Tonstad S. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies. Int J Epidemiol 2017; 46:1029-1056., depression²2 Liu X, Yan Y, Li F, Zhang D. Fruit and vegetable consumption and the risk of depression: A meta-analysis. Nutrition 2016; 32:296-302._, and excessive weight gain³3 Heo M, Kim RS, Wylie-Rosett J, Allison DB, Heymsfield SB, Faith MS. Inverse association between fruit and vegetable intake and BMI even after controlling for demographic, socioeconomic and lifestyle factors. Obes Facts 2011; 4:449-455..

Despite these benefits, overall, fruit and vegetable consumption are low in Brazil, especially among adolescents⁴4 Instituto Brasileiro de Geografia e Estatística (IBGE). Pesquisa Nacional de Saúde do Escolar (PeNSE): 2015. Rio de Janeiro: IBGE; 2016.^,55 Souza AM, Barufaldi LA, Abreu GA, Giannini DT, Oliveira CL, Santos MM, Leal VS, Vasconcelos FAG. ERICA: intake of macro and micronutrients of Brazilian adolescents. Rev Saude Publica 2016; 50:5s.. Data from the latest National School Health Survey (PeNSE, 2015) reiterated these findings in adolescents, since the consumption for at least five days a week of fresh fruits was reported by 32.7% and vegetables by 37.7% of the adolescents⁴4 Instituto Brasileiro de Geografia e Estatística (IBGE). Pesquisa Nacional de Saúde do Escolar (PeNSE): 2015. Rio de Janeiro: IBGE; 2016..

Given the increase in overweight rates and the low fruit and vegetable consumption in adolescents, intervention studies have been developed with the aim of acting in obesity prevention and in promoting healthy eating in this population group⁶6 Khambalia AZ, Dickinson S, Hardy LL, Gill T, Baur LA. A synthesis of existing systematic reviews and meta-analyses of school-based behavioural interventions for controlling and preventing obesity. Obes Rev 2012; 13:214-233.^,77 Cunha DB, Souza BSN, Veiga GV, Pereira RA, Sichieri R. Readiness for behavioral change and variation in food consumption among adolescents from a school-based community trial in Duque de Caxias, RJ. Rev Bras Epidemiol 2015; 18:655-665.. However, the effects of such interventions, in general, are less than desired⁸8 Evans CEL, Christian MS, Cleghorn CL, Greenwood DC, Cade JE. Systematic review and meta-analysis of school-based interventions to improve daily fruit and vegetable intake in children aged 5 to 12 y. Am J Clin Nutr 2012; 96:889-901.^,99 Evans CE, Ransley JK, Christian MS, Greenwood DC, Thomas JD, Cade JE. A cluster-randomised controlled trial of a school-based fruit and vegetable intervention: Project Tomato. Public Health Nutr 2013; 16:1073-1081.. This failure may be related to the fact that several aspects that make up the complex interrelationship of biological, environmental and psychosocial factors that influence the food consumption of adolescents are not considered in these interventions¹⁰10 Monge-Rojas R, Garita C, Sánchez M, Muñoz L. Barriers to and Motivators for Healthful Eating as Perceived by Rural and Urban Costa Rican Adolescents. J Nutr Educ Behav 2005; 37:33-40.. It has been shown that the release of information on food and nutrition alone are not enough to provoke changes in eating habits; therefore, intervention aiming to improve eating habits should apply further strategies to obtain positive results¹¹11 Mikkelsen BE, Ohri-Vachaspati P. Hunger, overconsumption and youth: future directions for research in school-based public health nutrition strategies. Publ Health Nutr 2013; 16(6):953-957.. Additionally, health promotion and the prevention of undesirable health conditions should also rely on information concerning psychosocial aspects, such as, social relationships, lifestyle, and satisfaction with life¹²12 Araujo EDS, Costa AJS, Blank N. Aspectos psicossociais de adolescentes de escolas públicas de Florianópolis/SC. Rev Bras Crescimento Desenvolv Hum. 2009; 19:219-225..

In this context, the psychosocial aspects involved in food choices can be important predictors of adherence to nutritional interventions to promote healthy eating. Studies that assessed the role of psychosocial factors related to food choices in adolescents have been carried out in different contexts¹³13 Tiedje K, Wieland ML, Meiers SJ, Mohamed AA, Formea CM, Ridgeway JL, Asiedu GB, Boyum G, Weis JA, Nigon JA, Patten CA, Sia IG. A focus group study of healthy eating knowledge, practices, and barriers among adult and adolescent immigrants and refugees in the United States. Int J Behav Nutr Phys Act 2014; 11:1-16.^,1414 Verstraeten R, Leroy JL, Pieniak Z, Ochoa-Avilès A, Holdsworth M, Verbeke W, Maes L, Kolsteren P. Individual and Environmental Factors Influencing Adolescents' Dietary Behavior in Low- and Middle-Income Settings. PLoS One 2016; 11:e 0157744., yet, in Brazil, these studies are still scarce and, until this moment, no similar studies were found. Thus, the present study aims to assess the association between psychosocial aspects and the fruit and vegetable consumption in adolescents.

Material and methods

This is a cross-sectional study carried out in a public school, selected by convenience, in the city of Niterói, Rio de Janeiro, Brazil. Were invited to the study all students between 10 and 19 years old enrolled from the 5^th to the 9^th grades. Adolescents with disabilities that prevented to obtain anthropometric measurements, pregnant adolescents, and those who were undergoing any treatment that required changes to the diet were not eligible to the study. From the 429 eligible students, 387 agreed to participate in the study and 327 (76.5%) presented complete information on food consumption and on psychosocial aspects related to the fruit and vegetable consumption, which were included in the present analysis.

Data collection was carried from August to December 2015. A self-administered questionnaire was applied using a PDA (Personal Digital Assistant) in the classroom, after guidance and under the supervision of the researchers. To guarantee the quality of the data, programming was carried out on the PDA that prevented the omission of answers. In addition, the questionnaires were revised when there was doubt or an answer considered inconsistent, the researchers confirmed the information with the respondents. Two 24-hour recalls (24hR) were applied and measurements of weight and height were taken.

Measurement procedures and data processing

Psychosocial aspects related to fruit and vegetable consumption habits

Psychosocial aspects were assessed using the questionnaire “Psychosocial Aspects Associated with Nutrition and Physical Activity of Adolescents”, developed by Monge-Rojas et al.¹⁵15 Monge-Rojas R, Nuñez HP, Garita C, Chen-Mok M. Psychosocial Aspects of Costa Rican Adolescents Eating and Physical Activity Patterns. J Adolesc Health 2002; 31:212-219.. This questionnaire was chosen for being developed specifically for adolescents and because it allows assessing simultaneously five psychosocial aspects (self-efficacy, family, peers, body image, and media/environment) related to food consumption. The questionnaire was submitted to cross-cultural adaptation study¹⁶16 Vasconcelos TM, Monteiro LS, Cunha DB, Sichieri R, Pereira RA. Reproducibility of a questionnaire on psychosocial aspects related to the consumption of fruit and vegetables in adolescents. DEMETRA 2022; 17:e59931.; therefore, the process of translation and adaptation of the questions followed the script proposed by Beaton et al.¹⁷17 Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the Process of Cross-Cultural Adaptation of Self-Report Measures. SPINE 2000; 25(24):3186-3191. and Reichenheim and Moraes¹⁸18 Reichenheim ME, Moraes CL. Operacionalização de adaptação transcultural de instrumentos de aferição usados em epidemiologia. Rev Saude Publica 2007; 41(4):665-673.. Along with the cross-cultural adaptation, a reproducibility evaluation and the assessment of the instrument’s multidimensional structure were also carried out, in order to confirm whether it could be applied to Brazilian adolescents. In this process, issues related to the “media/environment” dimension did not show acceptable psychometric indicators and were excluded¹⁶16 Vasconcelos TM, Monteiro LS, Cunha DB, Sichieri R, Pereira RA. Reproducibility of a questionnaire on psychosocial aspects related to the consumption of fruit and vegetables in adolescents. DEMETRA 2022; 17:e59931..

Additionally, the questionnaire was applied to a group of adolescents comparable to the study group, in order to assess the degree of difficulty in understanding and filling it out. Since some degree of difficulty was found, experts in nutrition and psychology revised and modified the instrument in order to make it easier to be completed by the adolescents. Then, another pre-test was carried out to verify the level of understanding of the instrument, which was, then, considered adequate.

The adapted questionnaire consists of 36 statements describing positive and negative behaviors related to the following dimensions: (a) family influence (8 questions); (b) peers influence (7 questions); (c) body image (9 questions); and (d) self-efficacy (14 questions) in relation to fruit and vegetable consumption. The adolescents were asked to assign each statement as true or false. For calculating scores, 1 (one) point was assigned for the answers in which positive behaviors were marked as “True” and for negative behaviors that were marked as “False”. Otherwise, that is, in case of a positive behavior marked as false or a negative behavior marked as true, the score for the question was zero (0). Thus, raw scores were estimated for each psychosocial aspect assessed by the sum of the points of each question, ranging from 0 to 14 for self-efficacy, 0 to 8 for peers, 0 to 8 for family and 0 to 10 for body image. To allow the comparison among the estimated scores for each aspect considered, the estimated raw scores were converted to values in base 10, which was performed using the “rule of three”. Thus, the raw score is multiplied by ten and the result is divided by the number of questions in each aspect evaluated by the questionnaire. Then, the scores in base 10 were standardized, considering the following steps: (1) for each psychosocial aspect, the mean and standard deviation (SD) of the score at base 10 were calculated; (2) for each individual, the base-10 score was reduced from the mean and divided by the standard deviation of the distribution. Therefore, the standardized scores means were equal to zero (0) and their variances were equal to one (1), so that the comparison among the different strata was in units of standard deviation.

These standardized values represent the individual score in units of the standard deviation. For the analyses on the association of psychosocial aspects with fruit and vegetable consumption, the standardized scores were categorized into less than or equal to the mean (score≤0), which represented less influence, and greater than the mean (score>0), representing greater influence of the studied aspect.

Food intake

Food intake was assessed using two 24-hour recalls. Additionally, three screening questions on fruit, vegetable (not counting potatoes and cassava), and salad frequency of consumption in the last month were asked, with the following response options: never or less than once a month; 1-3 times a month; once a week; 2-4 times a week; 5-6 times a week; once a day; and 2 or more times a day. The frequency of fruits, vegetables, and salad consumption in the last month was later categorized into: never or rarely (never or less than once a month), low or moderate frequency (once a month to four times per week), and high frequency (≥5 times per week).

A 24hR was applied in two non-consecutive days through an in-person interview conducted by nutritionists. Respondents were asked to report all food and beverages consumed during the day before the interview, which was conducted based on the Multiple Passage Method¹⁹19 Moshfegh AJ, Rhodes DG, Baer DJ, Murayi T, Clemens JC, Rumpler WV, Paul DR, Sebastian RS, Kuczynski KJ, Ingwersen LA, Staples RC, Cleveland LE. The US Department of Agriculture Automated Multiple-Pass Method reduces bias in the collection of energy intakes. Am J Clin Nutr 2008; 88:324-332. with the support of the computer program applied in the Study of Cardiovascular Risks in Adolescents (ERICA)²⁰20 Barufaldi LA, Abreu GA, Veiga GV, Sichieri R, Kuschnir MCC, Cunha DB, Pereira RA, Bloch KV. Software to record 24-hour food recall: application in the Study of Cardiovascular Risks in Adolescents. Rev Bras Epidemiol 2016; 19:464-468.. The mean usual intake of fruits and vegetables was estimated using the Multiple Source Method (MSM) to estimated means corrected by intra-individual variability²¹21 Harttig U, Haubrock J, Knüppel S, Boeing H. The MSM program: web-based statistics package for estimating usual dietary intake using the Multiple Source Method. Eur J Clin Nutr 2011; 65:S87-S91.^,2222 The German Institute of Human Nutrition [Internet]. [cited 2017 ago 17]. Available from: https://msm.dife.de/.
https://msm.dife.de... .

Weight status

Weight status was assessed based on Body Mass Index (BMI=weight/ height²). The adolescents were measured wearing light clothing and no shoes. Their weight was measured using a Tanita BC-558 portable electronic scale, with capacity for up to 150 kg and a variation of 50 g. Height was measured according to recommendations of Gordon et al.²³23 Gordon CC, Chumlea WC, Roche AF. Stature, recumbent length, and weight. In: Lohman TG, Roche AF, Martorell R, editors. Antropometric Standardization Reference Manual. Illinois: Human Kinetics Books; 1988. p.3-8. using a portable stadiometer (brand AlturaExata) with an extension of 200 cm and a variation of 0.1 cm.

Weight status was categorized into four categories (underweight, adequate weight, overweight, and obesity) based on the z-scores of the BMI to age and sex distribution curves proposed by the World Health Organization (WHO)²⁴24 De Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. Development of a WHO growth reference for school-aged children and adolescents. Bull World Health Organ 2007; 85:660-667.. Subsequently, for the analyses, the BMI was categorized as non overweight (underweight and adequate weight) and overweight (overweight and obesity).

Sociodemographic characteristics

Information about sex was self-reported and recorded in the PDA by the field researcher. Age was calculated as the difference between the date of data collection and the date of birth provided by the school and was categorized into two age groups: <13 years old and ≥13 years old.

Statistical analysis

The psychosocial aspect scores were described by raw and standardized medians for the total evaluated group and according to sex, age group, and weight status.

Daily usual consumption of fruits and vegetables, estimated through deattenuated means of two 24h-R, was described in means (and standard deviations) in grams per day (g/day). In addition, fruit, vegetable, and salad frequency of consumption was described by absolute and relative (%) frequencies, as well as weight status, sex, and age group categories. All estimates were stratified according to psychosocial aspects categorized into less than or equal to the mean (score≤0) and greater than the mean (score>0).

The Kolgomorov-Smirnov test was applied to verify the symmetry of continuous variable distributions. Psychosocial aspects and food intake variables were asymmetrically distributed and were tested by the Mann-Whitney and Chi-square tests (5% statistical significance). The Mann-Whitney test was used to verify possible differences among the values of the standardized median of psychosocial aspects according to gender, age group and weight status and for the analysis of the quantities of consumption of fruits and vegetables according to the evaluated aspects. The Chi-square test was applied to verify differences between the frequency of fruit and vegetable consumption according to psychosocial aspects. A statistical significance of 5% was adopted. Data were analyzed using the Statistical Package for Social Sciences (SPSS), version 19 (IBM SPSS Statistics).

Ethical aspects

The study was approved by the Research Ethics Committee of the “blinded”, under opinion No. 1.188.890, of August 17^th, 2015. Participation in the research was conditioned to the signing of the Term of Informed Consent by the guardian or individuals who were 18 years of age or older.

Results

Among the studied adolescents (n=327), 51% (n=165) were males, 32% (n=101) were overweight, and 54% were 13 years old or older, while the ages ranged between 10 to 16 years old (mean age=12.7 years old, SD=1.6) (Table 1).

From the 24hR data, it was estimated that the average daily consumption of fruits and vegetables was 36.2 g and 45.4 g, respectively (Table 1). It was found at 24hR, that only 29% of the evaluated adolescents reported consuming fruits, 52% consumed vegetables, and 63% consumed fruits and vegetables. Assessing exclusively adolescents who reported consuming fruits and vegetables, we observed an average consumption of 124 g and 87 g, respectively (data not shown). High frequency of fruit consumption (≥5x per week) was reported by 56% of adolescents, vegetables, by 68%, and salads by 53%. The analyses also showed that 18% of the students rarely consumed fruits and vegetables (never or almost never) (Table 1).

Self-efficacy (average of the standardized score=0.400) and the influence of peers (0.126) were the factors that influenced fruit and vegetable consumption the most in adolescents, since they showed higher medians in the standardized scores than the influence of body image (0.085) and the family (0.050). These findings were confirmed in the sex strata, both for females and males, in adolescents under 13 years old of age and in those who were not overweight (Table 2). However, for those aged 13 years old and over and those who were overweight, it was observed that the food choices for fruits and vegetables were basically influenced by peers (0.126). The self-efficacy scores showed significant differences for the age and weight status categories (Table 2).

Standardized scores greater than zero, which indicated greater influence of the psychosocial aspect, were observed for roughly 60% of the adolescents for all domains evaluated. Fruit and vegetable consumption was influenced by self-efficacy, as shown in Table 3. The usual average consumption of fruits (25.7 vs. 45.9 g/day) and vegetables (38.3 vs. 51.9 g/day), fruits and vegetables (68.2 vs. 99.8 g/day) was significantly greater among adolescents with higher self-efficacy (score>0), when compared to those with the lowest self-efficacy influence. Similar results were observed for fruit intake among adolescents with higher peer influence (score>0) compared to those less influenced by this aspect (25.9 vs. 42.8 g / day) (Table 3).

Regarding consumption frequency, it was observed that among the individuals who showed greater influence of self-efficacy and family (score>0) there was a significant higher proportion of individuals reporting high frequency of consumption of fruits (self-efficacy: 45.4 vs. 64.0%; family influence: 38.9 vs. 66.5%), vegetables (self-efficacy: 62.5 vs. 72.6%; family influence: 59.5 vs. 73.5%) and salads (self-efficacy: 41.4 vs. 64.6%; family influence: 38.2 vs. 64.3%) (Table 4).

Discussion

Among the adolescents investigated, the psychosocial aspects that influenced fruit and vegetable consumption the most were self-efficacy and peers. The influence of family and self-efficacy was associated with a higher consumption frequency of fruit, vegetable, and salad intake. Low consumption of fruits and vegetables was observed among the studied adolescents. Even among those who reported daily consumption of fruits and vegetables, ingestion represented only 30% of the 400-grams recommendation²⁵25 World Health Organization (WHO). Diet, nutrition and the prevention of chronic diseases. Geneva: WHO/FAO; 2003..

Subtle differences were observed in the influence of psychosocial factors on the consumption of fruits and vegetables for the estimates obtained by the 24hR (self-efficacy and peers) and by the screening questions (self-efficacy and family). We can consider that these results are complementary, since the 24hR and the screening questions capture particular aspects of the diet: mean intake and frequency of intake.

The reduced consumption of fruits and vegetables among adolescents has been observed in other Brazilian studies. Souza et al.²⁶26 Souza AM, Pereira RA, Yokoo EM, Levy RB, Sichieri R. Most consumed foods in Brazil: National Dietary Survey 2008-2009. Rev Saude Publica 2013; 47:190S-199S., studying data from the first National Food Survey (INA), found that adolescents were the only age group that failed to mention any vegetable among the 20 most consumed foods. Data from PeNSE (2015) showed that consumption of fresh fruits, at least five days a week, was reported by 32.7% of adolescents and vegetables, by 37.7%⁴4 Instituto Brasileiro de Geografia e Estatística (IBGE). Pesquisa Nacional de Saúde do Escolar (PeNSE): 2015. Rio de Janeiro: IBGE; 2016.. Souza et al.⁵5 Souza AM, Barufaldi LA, Abreu GA, Giannini DT, Oliveira CL, Santos MM, Leal VS, Vasconcelos FAG. ERICA: intake of macro and micronutrients of Brazilian adolescents. Rev Saude Publica 2016; 50:5s., evaluating ERICA data, also observed a low prevalence of fruit consumption, and found that fruits were among the 20 most consumed only among males aged 12 to 13 years old, mentioned by 18.0% of them.

The results of the present study are comparable to similar studies carried out with children and adolescents in other countries, which observed that self-efficacy and family influence were associated with fruit and vegetable consumption²⁷27 Pearson N, Griffiths P, Biddle SJH, Johnston JP, Haycraft E. Individual behavioural and home environmental factors associated with eating behaviours in young adolescents. Appetite 2017; 112:35-43.^,2828 Gebremariam MK, Henjum S, Terragni L, Torheim LE. Correlates of fruit, vegetable, soft drink, and snack intake among adolescents: the ESSENS study. Food Nutr Res 2016; 60:32512.. The results are also consistent with the findings by Salvy et al.²⁹29 Salvy SJ, De La Haye K, Bowker JC, Hermans RCJ. Influence of peers and friends on children's and adolescents' eating and activity behaviors. Physiol Behav 2012; 106:369-378. in a literature review on this subject, which indicated the importance of peer influence on healthy eating among children and adolescents. Pearson et al.²⁷27 Pearson N, Griffiths P, Biddle SJH, Johnston JP, Haycraft E. Individual behavioural and home environmental factors associated with eating behaviours in young adolescents. Appetite 2017; 112:35-43., evaluated 11-12-year-old adolescents in central Denmark schools and found that self-efficacy and social environment were significantly associated with the consumption of fruits and vegetables. Similar results were observed by Gebremariam et al.²⁸28 Gebremariam MK, Henjum S, Terragni L, Torheim LE. Correlates of fruit, vegetable, soft drink, and snack intake among adolescents: the ESSENS study. Food Nutr Res 2016; 60:32512., in a cross-sectional study with 742 adolescents from 11 secondary schools located in the Eastern part of Norway. The authors observed that self-efficacy related to healthy eating is positively associated with the consumption of fruits and vegetables. According to Pearson et al.³⁰30 Pearson N, Ball K, Crawford D. Parental influences on adolescent fruit consumption: the role of adolescent self-efficacy. Health Educ Res 2012; 27:14-23., self-efficacy is a strong predictor of healthy eating during adolescence. Thus, it highlights the importance of addressing self-efficacy in studies that aim to promote healthy eating in adolescents³⁰30 Pearson N, Ball K, Crawford D. Parental influences on adolescent fruit consumption: the role of adolescent self-efficacy. Health Educ Res 2012; 27:14-23.^,3131 Fitzgerald A, Heary C, Kelly C, Nixon E, Shevlin M. Self-efficacy for healthy eating and peer support for unhealthy eating are associated with adolescents' food intake patterns. Appetite 2013; 63:48-58..

According to Lubans et al.³²32 Lubans DR, Plotnikoff RC, Morgan PJ, Dewar D, Costigan S, Collins CE. Explaining dietary intake in adolescent girls from disadvantaged secondary schools. A test of Social Cognitive Theory. Appetite 2012; 58: 517-524., dietary self-efficacy is related to the perceived ability to make healthy food choices, even when facing an obstacle. It is noteworthy, that self-efficacy was associated with food choices and healthy eating behaviors in the present study. These findings were consistent with the results observed in other studies, which observed that knowledge about health associated with self-efficacy can be a more effective determinant for the choices of adolescents³³33 Pearson N, Ball K, Crawford D. Predictors of changes in adolescents' consumption of fruit, vegetables, and energy-dense snacks. Br J Nutr 2011; 105:795-803.^,3434 Pearson N, Ball K, Crawford D. Mediators of longitudinal associations between television viewing and eating behaviours in adolescents. Int J Behav Nutr Phys Act 2011; 8:23..

Another point that relates to the food choices of adolescents is the peers’ influence²⁹29 Salvy SJ, De La Haye K, Bowker JC, Hermans RCJ. Influence of peers and friends on children's and adolescents' eating and activity behaviors. Physiol Behav 2012; 106:369-378.. In the present study, the usual consumption of fruits was higher among adolescents with highest peer-influence scores. Similar results were found by Habe and Hartmann³⁵35 Hab J, Hartmann M. What determines the fruit and vegetables intake of primary school children? - An analysis of personal and social determinants. Appetite 2018; 1:82-91., who found that German children and adolescents ingested more fruits, when they realized that their friends also did. A study carried out with 2,764 European adolescents indicated that adolescents ingested healthy foods when their colleagues encouraged them to eat healthily, and this incentive stimulated a greater intake of fruits³⁶36 Stok F, De Vet E, De Wit J, Luszczynska A, SAfron M, De Ridder D. The proof is in the eating: Subjective peer norms are associated with adolescents' eating behaviour. Public Health Nutr 2015; 18:1044-1051.. Review studies suggest that peers could be possible targets in interventions promoting healthy eating diets among adolescents³⁷37 Chung SJ, Ersig AL, McCarthy AM. The Influence of Peers on Diet and Exercise Among Adolescents: A Systematic Review. J Pediatr Nurs 2017; 36:44-56..

Parents influence the eating habits of adolescents by being the providers, models and regulators of family nutrition. Studies indicate that adolescents who eat meals with their parents report better food regulation and selection than those who do not eat regularly with their parents or guardians³⁸38 Salvy SJ, Vartanian LR, Coelho J, Jarrin D, Pliner P. The role of familiarity on modeling of eating and food consumption in children. Appetite 2008; 50(2):514-518.^,3939 Hass J, Hartmann M. What determines the fruit and vegetables intake of primary school children? - An analysis of personal and social determinants. Appetite 2018; 1(120):82-91..

Limitations of this study refer to the methods used to assess food consumption which are dependent on the memory of the subjects. However, different strategies were used to reduce measurement errors, such as rigorous training of interviewers and the application of the 24R with the support of a computer program⁵5 Souza AM, Barufaldi LA, Abreu GA, Giannini DT, Oliveira CL, Santos MM, Leal VS, Vasconcelos FAG. ERICA: intake of macro and micronutrients of Brazilian adolescents. Rev Saude Publica 2016; 50:5s.^,4040 Alves MA, Souza AM, Barufaldi LA, Tavares BM, Bloch KV, Vasconcelos FAG. Padrões alimentares de adolescentes brasileiros por regiões geográficas: análise do Estudo de Riscos Cardiovasculares em Adolescentes (ERICA). Cad Saude Publica 2019; 35(6):e00153818. which is based on the multiple pass method¹⁹19 Moshfegh AJ, Rhodes DG, Baer DJ, Murayi T, Clemens JC, Rumpler WV, Paul DR, Sebastian RS, Kuczynski KJ, Ingwersen LA, Staples RC, Cleveland LE. The US Department of Agriculture Automated Multiple-Pass Method reduces bias in the collection of energy intakes. Am J Clin Nutr 2008; 88:324-332.. Two 24hR were also applied in non-consecutive days, allowing the estimation of usual consumption corrected by intra-individual variability. In addition, the results are compatible with findings from similar studies⁴4 Instituto Brasileiro de Geografia e Estatística (IBGE). Pesquisa Nacional de Saúde do Escolar (PeNSE): 2015. Rio de Janeiro: IBGE; 2016.^,55 Souza AM, Barufaldi LA, Abreu GA, Giannini DT, Oliveira CL, Santos MM, Leal VS, Vasconcelos FAG. ERICA: intake of macro and micronutrients of Brazilian adolescents. Rev Saude Publica 2016; 50:5s.^,2626 Souza AM, Pereira RA, Yokoo EM, Levy RB, Sichieri R. Most consumed foods in Brazil: National Dietary Survey 2008-2009. Rev Saude Publica 2013; 47:190S-199S., so it is believed that the results regarding the consumption of fruits and vegetables are reliable. Another limitation is the fact that the sample was selected for convenience, which compromises the extrapolation of the results to other populations. However, the size of the sample evaluated (n=327) allows to observe differences in the proportions of up to 10% among the strata evaluated, with 0.05 alpha and 80% power⁴¹41 Lwanga S, Lemeshow S. Sample Size Determination in Health Studies: A Practical Manual. Geneva: WHO; 1991..

A strength of this study is the fact that it uses a questionnaire developed specifically for adolescents, which simultaneously evaluates four psychosocial aspects related to the specific consumption of fruits and vegetables. This instrument was cross-culturally adapted and its reproducibility was analyzed in a similar sample to the one evaluated in this study¹⁶16 Vasconcelos TM, Monteiro LS, Cunha DB, Sichieri R, Pereira RA. Reproducibility of a questionnaire on psychosocial aspects related to the consumption of fruit and vegetables in adolescents. DEMETRA 2022; 17:e59931..

In Brazil, there are no studies that examine the role of different psychosocial aspects of food consumption in adolescents. This information is an important tool in understanding the factors that influence the eating habits of adolescents, especially in nutritional interventions. Intervention studies developed with the objective of promoting healthy eating in adolescents have limited impact⁶6 Khambalia AZ, Dickinson S, Hardy LL, Gill T, Baur LA. A synthesis of existing systematic reviews and meta-analyses of school-based behavioural interventions for controlling and preventing obesity. Obes Rev 2012; 13:214-233.^,77 Cunha DB, Souza BSN, Veiga GV, Pereira RA, Sichieri R. Readiness for behavioral change and variation in food consumption among adolescents from a school-based community trial in Duque de Caxias, RJ. Rev Bras Epidemiol 2015; 18:655-665.^,99 Evans CE, Ransley JK, Christian MS, Greenwood DC, Thomas JD, Cade JE. A cluster-randomised controlled trial of a school-based fruit and vegetable intervention: Project Tomato. Public Health Nutr 2013; 16:1073-1081.. Sichieri and Souza⁴²42 Sichieri R, Souza RA. Strategies for obesity prevention in children and adolescentes. Cad Saude Publica 2008; 24:S209-S234. suggest that the failure of these interventions may be related to the fact that they do not consider important aspects related to the individual, social, and family environment, which, in general, contribute to sedentary behaviors and caloric consumption above the required. According to Toral et al.⁴³43 Toral N, Conti MA, Slater B. Healthy eating according to teenagers: perceptions, barriers, and expected characteristics of teaching materials. Cad Saude Publica 2009; 25:2386-2394., psychosocial factors modulate the effect of nutritional interventions in terms of changing behaviors, attitudes and beliefs. The psychosocial factors associated with food consumption in adolescents is an important topic in the field of public health, which, however, has been little addressed in studies developed in the country⁴³43 Toral N, Conti MA, Slater B. Healthy eating according to teenagers: perceptions, barriers, and expected characteristics of teaching materials. Cad Saude Publica 2009; 25:2386-2394.. These findings are a contribution to future actions of healthy eating promotion targeting adolescents.

The study allowed us to identify that self-efficacy is the psychosocial aspects that had the greatest influence on the consumption of fruits and vegetables in adolescents, and that, under its influence, adolescents increase not only the amount but also the frequency of consumption of these foods. In addition, the findings of this study also showed the influence of peers on fruit consumption and the family’s influence on the frequency of consumption of fruits, vegetables and salad. These aspects should be considered when planning strategies that encourage the adoption of healthy eating habits, aiming to strengthen adolescents’ self-efficacy and work on the positive influence that peers exert, thus contributing to encourage healthy eating.

Acknowledgments

The Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) provided financial support to the researchers, process No. 471282/2012-0 and 400793/2014-8.

To professor Rafael Monge-Rojas, from the Instituto Costarricense de Investigación y Enseñanza en Nutrición y Salud (INCIENSA), for making available the questionnaire used in the study and the for the support offered.

References

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