Effect Of A Middle School Physical Activity And Healthy Food Intervention On BMI Z-scores

Abstract

Interventions to prevent overweight intended to increase physical activity and to improve children's diet. The school setting offers several opportunities for preventing overweight. Schools have contact with parents and parental involvement can be important in overweight prevention. However, most of the previous school-based interventions were conducted in elementary schools and were not effective in reducing fatness or weight gain. PURPOSE To evaluate the effect of a school-based physical activity and healthy food intervention, designed to prevent the increasing prevalence of overweight and to look at the effect of involving parents. METHODS A random sample of 15 schools was randomly assigned to three conditions: intervention with parental support, intervention without parental support condition and a control condition. Two schools were left out of analyses because they did not meet the minimum intervention criteria. A total sample of 2141 7th and 8th graders (age 13.06 ± 0.82y) was enrolled in this study. The intervention was implemented over 1 school year and included environmental and personal modifications, related to food choices and physical activity behaviour. Measures were assessed in September 2003 and repeated in June 2004. Weight and height were measured to calculate body mass index (BMI). On the basis of the Flemish reference data BMI z-scores were calculated using the LMS method, taken age and gender into account. Repeated measures ANOVAS were used to evaluate the intervention effect. RESULTS When comparing the intervention with parental support condition with the control condition, there was a significant time by condition interaction effect for BMI z-scores in girls (F=8.87, p<0.01) but not in boys (F=1.67, p=0.196). In girls, increase in BMI z-scores was lower in the intervention with parental support condition (0.06 ± 0.05) compared to the control condition (0.12 ± 0.05). No significant time by condition interaction effects for BMI z-scores were found when comparing the intervention without parental support with the control condition in both boys (F=3.01, p=0.08) and girls (F=0.08, p=0.78). CONCLUSIONS The intervention with parent involvement was effective in reducing increase BMI z-scores in girls, but not in boys. Involvement of the parents is important to increase the effectiveness of the intervention. Supported by the Flemish Government.