With principal component analysis, three major dietary patterns were identified for the study participants. Among girls we found significant relationships between adherence to healthy pattern and BMI. Overweight girls were more likely to have a western or sweet-dairy pattern. No significant association was found regarding western and sweet-dairy patterns and weight status for schoolboys. Children adhering to a healthy pattern were more likely to have higher-educated mothers.
Studying characteristics of overall diet results in the examination of the combined nutrients effects on health and better prediction of diet-disease relationships.[37
] To our knowledge, this is the first study to examine the associations of major dietary patterns with weight status in a large group of school-children. The previous dietary pattern studies in Iran mainly have conducted on adults[20
] and limited information is available about dietary patterns of children, considering overweight/obesity and lifestyle factors, however, there are few publications of Iranian adolescents group.[23
Comparing dietary patterns between studies is somewhat difficult due to differences in dietary assessment and rotation methods, food groups used in the factor analyses, the number of patterns should be retained for analyses and the statistical techniques.[28
Despite inconsistencies between the results derived from different studies, there are some similarities regarding dietary patterns identified among children. Moreira et al
] explained 8 dietary factors with similar components to the present study, such as dietary pattern 1 contained plant foods, highly loaded for fruits, vegetables, legumes and olive oils, dietary pattern 4 included fast foods, sugar-sweetened beverages and pastry, dietary pattern 6 with higher factor loadings for dairy products (yogurt, milk, and ice-cream), dietary pattern 7 included higher amounts of crackers, cookies and pastry. Shin et al
] reported 3 major dietary patterns labeled a Korean healthy pattern, an animal foods pattern and a sweet pattern. McNaughton[40
] identified 3 major dietary patterns, two of them similar to the present study; high fat and sugar pattern and vegetable pattern. Similar patterns have also described by Northstonne, named as snacking pattern[41
] and Nobre et al
., labled as “mixed diet,” “snack” and “unhealthy” patterns.[42
] Food items loaded in these patterns were mostly similar to our study.
In the present study, we found that girls in the second quartile of healthy pattern tend to be overweight compared to their counterparts in the highest quartile. It is may be due to the nutrient content of healthy diets such as fiber, showing the protective effect against obesity.[43
] Among schoolchildren with high-educated mothers, healthy pattern scores were higher. These are in line with previous studies emphasizing the important role of education in consuming foods with plant origin mostly defined as healthy and avoiding poor nutrient and high-density foods. In addition, this could be due to the more direct interactions of child-mothers than do fathers.[27
Following a Western or sweet-dairy eating pattern in the second quartile, girls had a significantly lower likelihood of being overweight compared to the fourth quartile, however, these associations were not seen among schoolboys. These discrepancies might be due to gender differences in diet, misreporting of energy intakes, particularly in the overweight and obese children,[45
] food items eaten during the day, residual errors even after adjustment for covariates, or other unknown confounders. Any under-reporting of unhealthy food items would be able to attenuate the association between unhealthy eating pattern and overweight. We also found that boys with lesser adherence to a healthy pattern, were less likely to be overweight, similar to this has shown in two previous studies.[27
] Another research showed children adhering to a junk/convenient eating pattern, had a significantly lower likelihood of being overweight.[29
] This may partly be explained by over-reporting of healthy dietary habits such as fruits and vegetable consumption among overweight children or adoption of healthier behavior to control their weight.
As mentioned earlier, the sweet-dairy components were eggs, butter, honey, jam, snacks (e.g., chips, crackers, corn puffs) along with others, which had lower loading factors indicating less consumption, such as dried fruits, tomatoes and fruit juices. This shows that substituting of the latter could be possible because these items are eaten together on a regular basis as a food pattern. Improvement of parents and child's attitude and knowledge will provide better nutrition.[47
There are some resemblance between our results and those reported from Korean children showing no associations for healthy and sweet patterns with overweight.[39
] Several previous reports are in accordance with our findings; four longitudinal studies reported no significant association between milk pattern and BMI.[48
] On the contrary, positive association was found between overweight/obesity and food patterns that included high amounts of milk among Portuguese children.[26
] Therefore, evidence is inconclusive regarding dietary patterns and weight status of children.[49
The nutrition transition besides rapid socio-economic changes in Iran makes the opportunity to adopt a more westernized food patterns especially for children and adolescents who their preferences mostly are based on taste, palatability and the availability of fast foods.[15
] Alongside, sedentary lifestyle habits related to adhering western dietary pattern were found among children. Time spent on sedentary activities such as watching TV, for more than the recommendations of the American Academy of Pediatrics[50
] (up to 2 h/day) was related to higher scores of western dietary pattern. Previous studies are consistently in line with these relations. Salmon[51
] and Story[52
] concluded that increased TV viewing was associated with unhealthy eating pattern, including higher consumption of pizza, sodas and snack foods, supporting some other reports.[24
Longer sleep duration was significantly associated with higher consumption of food from healthy pattern and inversely related to sweet-dairy pattern among boys, consistent with the results of Portuguese schoolchildren[26
] and children from Finland.[54
] These findings are of particular interest since sleep deprivation, prevalence of overweight/obesity and increased appetite were correlated in children and adults.[26
It is important to highlight this is the first report exploring the associations between dietary patterns, socio-demographic characteristics, physical activity, sleeping and weight status, adjusting for confounders. However, the interpretation of these results needs to consider the following limitations. First, data driven by factor analysis depends on subjective or arbitrary decisions, for example, when grouping the food items or labeling of the factors.[56
] Second, this method is data-specific; therefore, generalization of our findings to children living in rural districts, Iranian children, as a whole, or other populations is limited because of differences in dietary and lifestyle habits.
Third, nutritional intakes of children estimated via a semi-quantitative FFQ might not represent their true intakes and may depend on recall bias and social desirability,[57
] however, it is an appropriate instrument for ranking dietary intakes. Furthermore, misclassification of the children's dietary intake, resulted from administration of the FFQ to the student's mothers, might happened especially of foods eaten away from home. Thus according to Drewnouski,[58
] these dietary data may consider as the mother's dietary image rather than the absolute diet of the child. However, cognitive skills required to estimate and recall usual intakes, are a great challenge for elementary school children.[59
] Furthermore, the etiology of overweight/obesity is complex, thus some unknown confounders might play a role in the study results. Conclusions about causal relations are not possible because the study was cross-sectional in nature. Prospective studies are warranted to confirm these associations.