Research Subjects
In this cross-sectional study, 580 schoolchildren aged 7-12 years were recruited from May to September 2021 using a multistage cluster sampling method as a representative sample of children living in urban areas of Zabol, Sistan and Baluchestan provinces in southeastern Iran. First, schools were selected as clusters, and then school classes were considered as strata. After that, children were randomly selected from the list of student records in each class.
The sample size of this study was calculated based on information obtained from the study by Shahraki et al.15Considering the 95% confidence interval (figure), with a precision of 3% (d), and the prevalence of stunting was 16% (p), it was calculated that 574 subjects should be included in the study. Estimating a non-response rate of 5%, 602 children were invited to participate in the study. Inclusion criteria were age between 7 and 12 years and the willingness of the children’s parents to participate in the study. Exclusion criteria included taking medications, following specific diets, and having genetic or chronic diseases. After excluding children with incredibly high energy intakes of less than 500 kcal/day and more than 4000 kcal/day (12 boys and 10 girls), 580 children remained for analysis.
Demographic data and anthropometric measurements
General characteristics of the children and their parents, including age, sex, parental education level, parental occupation, household size, and number of children in the household, were obtained through face-to-face interviews with the children’s mothers by two trained research assistants using questionnaires.
Participants’ weight was measured using a Beurer digital scale (Beurer BF66, Germany) while wearing light clothing and without shoes, and their height was measured with a tape measure to within 0.1 cm while standing without shoes. Body mass index (BMI) was calculated as weight (kg) divided by height squared (m).2The scale was always zeroed before any measurements were taken. All measurements were taken by the same person to minimize subjective errors.
Dietary intake assessment
Dietary intake was assessed using a semi-quantitative food frequency questionnaire (FFQ) containing 168 food items specifically designed and validated for the Iranian population.14The good validity and reliability of the FFQ in assessing nutrition and food intake in Iranian children has been previously reported.16The FFQ also assessed eating behaviors related to children’s diet quality, including use of sugar-sweetened beverages, sweet snacks, salty snacks, and frequency of fast food intake.
Trained research assistants interviewed the children and their mothers and administered all questionnaires. Mothers were asked how many specific servings of each food their children had consumed each day during the previous year (for example Bread), weekly (for example rice, milk), or monthly (for example The research assistants used a calibrated home-use measuring device (for example cups, glasses, bowls, plates, spoons, ladles, etc. Quantities of food consumed were then converted to grams using a household scale. Food intake was then converted to energy and other nutrients using the Nutritionist-IV (N4) software program (version 7.0, N-Squared Computing, Salem, OR, USA).17,18was modified for Iranian cuisine, allowing us to code almost any food eaten by the subjects. If a particular ethnic dish was not in the N4 database, it was coded as a similar item.
Assessing adherence to the modified Adolescent Healthy Eating Index
Participants’ adherence to healthy dietary guidelines was assessed using the MYHEI scoring system. Briefly, the MYHEI consisted of 10 components: whole grains, fruits, vegetables, dairy products, percentage of meat, sugar-sweetened beverages, butter and margarine, sweet snacks, salty snacks, and fast food. In the MYHEI scoring system, a higher intake of five components (whole grains, fruits, vegetables, dairy products, and percentage of meat) and avoidance or reduction in the remaining five components (sweetened beverages, butter and margarine, sweet snacks, salty snacks, and fast food) indicate a healthier diet. Each component was scored from 0 (not adherent) to 10 (fully adherent), with intermediate scores calculated to indicate the degree of adherence to dietary recommendations. The scores of all components were summed to calculate a total MYHEI score, which ranged from 0 to 100, with higher scores indicating a healthier diet. The scoring criteria for each component are summarized in Table 1.
Assessment of nutrition outcomes
The study investigated underweight, stunting, and wasting as nutritional outcomes among participants. Children’s nutritional outcomes were assessed by calculating Z-scores for weight-for-age (WAZ), height-for-age (HAZ), and BMI-for-age (BAZ) according to the World Health Organization (WHO) growth standards 2007 (5–19 years) (WHO 2007). Z-scores for these nutritional indicators were calculated using the WHO Anthro Plus software program (version 1.0.4).19Child underweight, stunting, and wasting were considered as WAZ, HAZ, and BAZ, respectively, less than two standard deviations (Z score < −2SD) below the median of the reference population (growth standards, WHO 2007).19.
Statistical analysis
Data were analyzed using IBM SPSS version 25 (IBM Corp., Armonk, NY, USA). Participants were classified into the following quartile categories based on the cut points of the MYHEI: 1st, < 47.5; 2nd, 47.5 to < 54.5; 3rd, 54.5 to < 64.4; 4th, ≥ 64.4. The Kolmogorov–Smirnov test was applied to determine the normality of the data. Results were presented as mean ± standard deviation for quantitative data with normal distribution and frequencies (percentages) for qualitative data. Significant variations in anthropometric measurements and general characteristics between MYHEI quartile groups were assessed by ANOVA with Tukey's post hoc test. Pearson's chi-square (χ2) tests were employed across MYHEI quartile groups for qualitative data.
Age-, sex-, and energy-adjusted nutrient and food group intakes were compared across MYHEI categories using analysis of covariance (ANCOVA) with Bonferroni correction. Kruskal-Wallis tests were used to compare numerical variables with non-normal distributions. Associations between MYHEI component scores and nutrition outcomes among participants were also explored by ANCOVA after adjusting for age, sex, and energy intake. Multivariate logistic regression was used in crude and adjusted models to examine the relationship between MYHEI and odds of underweight, stunting, and wasting. In adjusted models, important factors such as age (years), sex (boys/girls), and energy intake (kcal/day) were controlled. In all multivariate models, the fourth quartile (QFourThe association between increasing MYHEI quartile category and increasing prevalence of nutrition outcomes was assessed for overall trends using the Mantel-Haenszel extended test. Logistic regression results are expressed as adjusted odds ratios (OR) with 95% confidence intervals (CI). p-values < 0.05 were defined as significant.
Ethics approval and consent to participate
All methods and procedures performed in this study conformed to the guidelines of the Declaration of Helsinki and were approved by the Ethics Committee of Zabol University of Medical Sciences (ethics code: IR.ZBMU.REC.1401.006). Before the start of the study, the children’s parents were fully informed about the study’s aims and protocol. Parents and guardians provided written informed consent for their children to participate in the study. Parents were informed that they could withdraw their consent to participate at any time.
