Relationship between dietary patterns with body mass index, waist circumference and blood pressure among secondary school children in Mashhad, Iran

Obesity is a public health concern across developed and developing countries. In Iran, cardiovascular diseases are leading cause of death, while obesity and blood pressure, both are related to them. However, there is a lack of study on the relationship between dietary patterns, obesity and blood pressure among adolescents in Iran. The purpose of this study was to identify major dietary patterns of adolescents and to examine the relationship between dietary patterns with body mass index (BMI), waist circumference (WC), and blood pressure (BP) among secondary school children (12-14 years) in Mashhad, Iran. Dietary intake is an important determinant of obesity and blood pressure. The dietary pattern approach considers the overall diet of person by taking into account intake of combined food and nutrition. This cross-sectional study of 1189 secondary school children (579 males and 610 females) aged 12-14 years old were selected through a stratified multistage random sampling, was conducted in urban low and high socio-economic area of Mashhad. Dietary intake was assessed by interview using semi-quantitative food frequency questionnaire (FFQ) with 121 items, 24-hour dietary recall, and food record. All adolescents were measured for weight and height, then measurements were used to calculate BMI based on the formula: BMI= Body Weight (kg) / Height (m2). BMI were categorized using the World Health Organization cut-off points (WHO, 2007). Blood pressure was determined and classified based on cut-off points (NHBP, 2004). The Principal Component Factor analysis was applied to drive dietary patterns. Twenty nine (29) food groups were entered into the factor analysis. Logistic regression analysis was used to calculate odds ratio (OR). An exploratory factor analysis resulted in two types of dietary patterns that accounted for 26.6% of the total variance for the original dietary intake. Healthy dietary pattern was characterized by higher intake of fish and other sea foods, fruits, and fruit juice, green, white and yellow vegetables, whole grains, dried and processed fruits. The Unhealthy dietary pattern was heavily loaded on sweets, sugars and confectionary, tea, and coffee, egg, cooked, and fried potato, and moderately loaded on snacks, nuts, Iranian broth, and pickles. Household socio-demographic information, lifestyle factors, eating and meal patterns parental BMI and dietary patterns was determined. Parents’ weight and height were self-reported by them. All statistical analyses were performed using the Statistical Package for Social Sciences (SPSS 17) for windows. All variables were tested for normality by Kolmogorov-Smirnoff. The level of significance for all statistics was set at p< 0.05 levels and all analyses were two-tailed. Descriptive statistics was used to summarize continuous variables using mean, standard deviations and frequencies. Multivariate logistic regression was used to identify the association between independent variables and outcome variables (child’s BMI, WC, and BP) while controlling for potentially confounding variables. The overall prevalence of overweight and obesity among secondary school children in Mashhad was 17.2% and 11.9%, respectively. A higher proportion of male (30.7%) than female (27.4%) children were overweight or obese. BMI of the children was significantly related to gender (p= 0.02), birth order (p<0.01), parents' education level (p< 0.001), father's employment status (p< 0.001) and family monthly income (p< 0.001). Other variables such as TV watching duration among males (P=0.002), eating behaviors, several eating restraint items, dietary patterns (p< 0.001), and parental BMI (p< 0.001) were significantly associated with BMI. Furthermore, variables like eating restraint, eating behaviors, TV watching in males (p=0.003), BMI (p=0.001), WC (p=0.04), and dietary patterns (p=0.01) showed significant association with blood pressure. The high prevalence of overweight and obesity among secondary school children as compared to previous studies in Iran could be related to the changing lifestyle of the population as reflected in the selected socio-demographic factors. The strong relationship to parental BMI was probably related to a combination of genetic and lifestyle factors. Strategies to address childhood obesity should consider the interaction of these factors and its impact on lifestyle behaviors of children and adolescent