In reply
We appreciate the kind comments of Drs Krul and van Leeuwen regarding our study. They suggest that the informational newsletter may have contributed to or interacted with differences among families of low and high SES to reduce age- and sex-standardized BMI (zBMI). The intervention included a behavioral engineering device to reduce sedentary behavior as well as newsletters that were written at the eighth-grade level. It is possible that the newsletter interacted with the behavioral engineering device to reduce television watching and computer use to differentially reduce zBMI. Families of lower SES may have benefitted more from the information in the newsletter than families of higher SES, who may have already known some of this information. Krul and van Leeuwen also note that the families of higher SES showed greater zBMI changes than the families of lower SES, independent of group assignment, and they wonder whether this may have been due to the newsletters. While the families of higher SES did show larger overall zBMI reductions, the differences between the families of lower SES in the intervention group were not significantly different from the differences for the families of higher SES in the control or intervention groups at 2 years (− 0.19, − 0.22, and − 0.27 zBMI units, respectively). Newsletters were provided to both the intervention and control groups, but the newsletters were different between the groups. The newsletter for the intervention group included ideas about how television influences children and suggested ways to modify their environment and also included parenting tips, recipes, and activities, while the control-group newsletter provided no information on television and how it affects children or ways to change one's environment. Research is needed to determine the contribution of the newsletters when combined with a behavioral engineering device for preventing obesity in young children of lower SES and to determine whether families of higher SES could benefit from information provided in the control newsletter to reduce television watching and zBMI without the behavioral engineering device.