Childhood Obesity: Sibling Influence May Be Greater Than Parents

Mark C. Pachucki, PhD Senior Scientist, Mongan Institute for Health Policy Affiliated Faculty, MGHfC Division of General Academic Pediatrics Instructor in Medicine and Pediatrics, Harvard Medical School Boston, MA Interview with:
Mark C. Pachucki, PhD
Senior Scientist, Mongan Institute for Health Policy
Affiliated Faculty, MGHfC Division of General Academic Pediatrics
Instructor in Medicine and Pediatrics, Harvard Medical School
Boston, MA 02114

MedicalResearch: What are the main findings of the study?

Dr. Pachucki: We found that in in one-child families, having an obese parent made a child about twice as likely to be obese themselves. However, in two-child families, a child’s obesity status was more strongly related with their sibling than with their parent. Even more interesting, in the case of the younger sibling, the parent’s obesity status was not related with that child’s obesity status at all. These findings matter because family members are primary sources of social influence for children – understanding how health status is correlated within a family gives us a better foothold on possible intervention strategies.

MedicalResearch: Were any of the findings unexpected?

Dr. Pachucki: We’ve known from prior research that there’s a strong parent-child obesity link, and separate studies have shown that there’s a strong sibling-sibling obesity correlation as well. Parents model healthy and unhealthy behaviors for their children through their own actions; siblings do this as well. So it wasn’t immediately clear which kind of obesity relationship would be stronger. I went into this with a hunch that given parents’ oversize roles in their kids’ lives, parent-child obesity would be stronger than sibling-sibling obesity, but I was surprised that it was the opposite. What’s also interesting is that if siblings were of the same gender, it made a big difference in their shared obesity status. Having an older brother who is obese makes it more likely that a younger brother will also be obese. For girls, the pattern was the same – having an obese older sister increases the odds that the younger sister will be obese.

MedicalResearch: What should clinicians and patients take away from your report?

Dr. Pachucki: Our health is often more connected with the other people in our lives than we commonly recognize. Clinicians should continue to pay close attention to the health status and behaviors of other people in a child’s family. For adult patients who have children, our message isn’t that your health doesn’t matter to your child’s health, but that during a child’s development, their siblings may play a greater role in their health behaviors and health outcomes. For child patients, our message is that if they make efforts to eat healthy food and get enough exercise, it can also improve the health of their brother or sister.

MedicalResearch: What recommendations do you have for future research as a result of this study?

Dr. Pachucki:: This was a relatively modest study concerned with reported behaviors, and it would be great to replicate it on a larger scale with more detailed information on family members’ measured food intake, physical activity and weight status. We also recognize that obesity is a result of a mix of behavioral, social, and genetic factors, and we could only look at part of the puzzle. Our study was a cross-sectional snapshot at one point in time, and we examined correlations, not causal relationships. Longitudinal data could provide stronger evidence of sibling or parental responsibility for a child’s health. More concrete knowledge in this area would help us use information about relationships to improve family-based obesity interventions.


Within-Family Obesity Associations
Pachucki, Mark C. et al. American Journal of Preventive Medicine



Last Updated on July 8, 2014 by Marie Benz MD FAAD