The present study aimed to explore the mechanisms through which parental education differences are associated with children’s body composition. Current results first confirmed that parental educational level was inversely associated with children’s BMI and waist circumference. Next, the results showed that the association between parental education and children’s body composition was partially mediated by certain EBRBs, namely breakfast consumption, sports participation, TV viewing and computer use. Additionally, a suppression effect was found for sugared drinks intake. No mediation effect was found for active transportation and sleep duration.
Although previous studies looked at the separate relationships and not at the mediation effect, the results are in line with previous reports in which higher parental education was associated with lower childhood overweight indices [29, 30]. The associations between parental education and the EBRBs are also in line with available literature showing a negative association between several SES-indicators (including parental education) and breakfast skipping , sedentary habits , sugared drinks intake  and active transportation , and a positive association between SES and physical activity .
The current results on the association between the different EBRBs and the body composition outcomes are also in agreement with previous reports. Physical activity level, TV viewing, sugared drinks intake, breakfast consumption and sleep duration have been clearly associated with childhood overweight, while computer use was found to be related only in some studies [9, 35–38]. Previous reports on the association between active transportation and overweight did not show a consistent relationship [18, 39].
Although sleep duration has been associated negatively with childhood overweight – which was also confirmed in the present data-, the current analysis did not show a mediation effect of sleep duration, due to a non-significant association between parental education and sleep duration. In contrast, parental education was associated with active transportation, but active transportation was not associated with body composition indices. Recent reports showed positive associations between parental education and cycling to school while negative associations between cycling to school and overweight have been reported [40, 41]. Therefore, the single mediation analysis was also repeated for the two active transportation categories separately, in order to look at the specific trends. We found a negative association between parental education and walking to school but no association between parental education and cycling to school. In both cases no association with body composition indices was found (data not shown).
A suppression effect was found for sugared drinks intake. This effect could be due to a lower intake of sugared drinks in overweight children, or a higher impact of underreporting in this group [42–44]. It is also noteworthy that sugared drinks consumption was a suppressor only in the BMI model, but not in the waist circumference model.
The analyses included two different body composition indicators, namely BMI and waist circumference. The significant mediators explained 36% of the relationship between parental education and waist circumference, while only 19% of the relationship between parental education and BMI was explained. This finding could reflect the differences between BMI and waist circumference as measures of childhood adiposity. Waist circumference has been observed in cross-sectional studies to be a good abdominal fat estimate , a better predictor of cardiovascular disease risk factors in childhood [46, 47], and to predict cardio-metabolic health risk in adults beyond that explained by BMI [48, 49].
To our knowledge, this is one of the first studies trying to disentangle the complex interaction between parental education, several EBRBs and children’s body composition by applying mediation analysis. The proportion of the associations explained by the included mediators in both models was moderate, remaining the direct associations (c-path) still significant after adjusting for the mediators (c’-path). These results suggest that other variables not included in the analyses may play a mediating role in the relationship between parental education and children’s body composition. Future analyses including other potential mediators, not only behavioral but also environmental factors, like availability or accessibility, could enhance the knowledge about the complex relationship between parental education and children’s body composition.
It has to be kept in mind that this study is subject to some limitations. First, this concerns a cross-sectional study providing evidence for associations but not causation. Further, data on dietary, physical activity and sedentary behaviors were based on self-reports, and thus possibly biased. However, the measures showed good test-retest reliability and construct validity [23, 24]. When considering sedentary behaviors it is also important to note that some sedentary activities, like reading or studying were not included in the present study. Is therefore possible that questionnaires did not reflect the real, total time spent in sedentary behaviors. Parental education was reported taking into account both parents, and therefore we were not able to assess the differential influence of paternal and maternal educational levels on children’s EBRBs. Although the use of central adiposity indicators like waist circumference is useful as a good predictor of future health problems, it could be helpful to control for the maturation level when assessing pre- and adolescent population . Unfortunately, no information on maturation level was collected in the ENERGY cross-sectional study. Finally, the differences between selected participants and those not included in the analysis may influence the generalizability of the results. However, differences were small and, although significant, probably not relevant.
Strengths of the present study include the large multinational sample from different regions across Europe, the available measured weight, height and waist circumference and the standardized data collection protocol across the different centers.