The article by Van den Berg et al (2011) titled discusses issues relating to childhood body mass index i.e. overeating, impulsivity and reward responsiveness. The authors do not categorically state their research questions in the study. However, it can be deduced from their hypothesis that they sought to find how impulsivity and reward responsiveness influence body mass index (BMI) through overeating in children. The lack of a null hypothesis to counter the alternative hypothesis is a major weakness of the study, because there is testing of the potential lack of association between impulsivity, reward responsiveness and BMI in children as a result of overeating.
The researchers developed extensive questionnaires that were handed to children in 11 primary schools throughout the Netherlands to seek participation of their parents in the study. The questionnaires contained questions on early growth, physical activity, medical condition of children, their strengths and difficulties, children’s sensitivity to punishment and reward, the children’s eating behavior, physical attributes of child’s family, education level of parents, and family history of type 2 diabetes and obesity. The study design is appropriate: it is customized for the specific population, has well-defined or appropriate pediatric-relevant endpoints. However the study design was not realistic enough to be accepted by many parents (only 500 out of about 1450 parents contacted).
The study used random sampling to target children in grades 1-6 or an approximated equivalent of 1450 parents. Researchers sent letters to the parents describing the study and managed a sample of 500 parents who gave consent for participation. 83.4% of the sample (417 parents) completed the questionnaire. The sample size was adequate relative to the objectives of the study (van den Berg et al., 2011).
A total of 346 children (193 boys and 153 girls aged 6-13 years) were entered into analysis. The analysis excluded children with known type 1 diabetes, celiac disease, sibling participants, and parents who did complete the Children’s Eating Behavior Questionnaire and the Sensitivity to Punishment and Sensitivity to Reward Questionnaire for children. SPSS version 16.0 was utilized for all statistical analyses while Baron and Kenny’s (1986) mediation analysis was used in testing the hypothesis. Better testing of the hypothesis would have possible using more robust tests of mediation such as the Current Index to Statistics or Monte Carlo studies.
The results of the study showed high impulsivity in boys compared to girls and no significant differences in eating between boys and girls. Obese children scored highly in overeating than other BMI classes. On reward responsiveness, obese children scored highest followed by overweight, normal weight, and underweight children respectively. The results show that impulsivity and reward responsiveness are positively associated to BMI in children in terms of eating. The results can be generalized to the larger population.
Reference:
van den Berg L, Pieterse K, Malik JA, Luman M, Willems van Dijk K, et al. (2011). Association between impulsivity, reward responsiveness and body mass index in children. Int J Obes (Lond) 35: 1301–1307.
