By William Stratbucker, medical director, Healthy Weight Center, Grand Rapids, Michigan

We know that a child’s peer group influences their behavior, particularly teenagers. If adolescents hang out with kids who engage in risky behavior, they are more likely to engage in such behavior themselves. We also learned about the influence of social networks on adult obesity in a 2007 landmark study published in The New England Journal of Medicine. In that study, researchers found that an individual’s chance of obesity increased 57% if they had a friend who also became obese; with increased risks of 40% for someone with an obese sibling and 37% for someone with an obese spouse. It is almost as if obesity were spread like a flu virus.

Now comes evidence that similar relationships occur between school-aged children. Researchers from Vanderbilt University collected data from elementary-school aged children participating in after-school care (mean age 7.86), mapping their social networks and physical activity levels.

They found that children’s friendships “heavily” influenced their level of physical activity. In fact, it was the greatest influence on the amount of time children spent in moderate-to-vigorous physical activity during those after-school hours, with kids changing their own levels to match those of their friends. However, children did not end their friendships with children who did not match their own activity levels, nor did they deliberately choose friends whose activity levels matched their own.

I found this study fascinating. If you think about it, it suggests that if you put a physically active kid in with a group of sedentary children, the risk is that the majority rules and the active kid becomes sedentary. Conversely, if you put an inactive kid in with a group of active kids, you might see that child become more active. The problem is that if you have an active kid at home but put him/her in after-school care with a bunch of inactive friends, there is the risk that the child will not be active during that time. Thus, it becomes even more important for instructors/leaders and parents to promote physical activity in such programs.

As pediatricians, we are always looking for more behavioral strategies to use when counseling families about healthy lifestyles. So this is an important study to share with parents. They should understand the influence a child’s peer group has on his/her physical activity levels. For instance, if they have a sedentary child they might want to consider signing him/her up for a team sport, where the child can make friends who are more physically active.

The study also shows the importance of the after-school environment in kids’ activity levels. This is an incredibly important time for kids to engage in physical activity during the school week. If this “break” time is filled with inactivity like screen time followed by homework children end up with no time for activity.

As you know, screen time during the school week is an enormous problem. Estimates are that most children spend 1 to 3 hours a day watching TV, playing video games, or on their computers, and that the amount of screen time is directly related to the risk of obesity.¹

Thus, encouraging parents who need to put their children into an after-school environment, that it be one that encourages physical activity, is an important message for community pediatricians to convey.

William Stratbucker is medical director of the Helen DeVos Children’s Hospital Healthy Weight Center in Grand Rapids, Michigan.

How do you think parents can encourage their children to develop activities with more physically active children?

1. Marshall SJ, Biddle SJ, Gorely T, Cameron N, Murdey I. Relationships between media use, body fatness, and physical activity in children and youth: a meta-analysis. Int J Obes Relat Metab Disord 2004;28(10):1238-46.

By Tom Peterson, MD, Executive Director, Safety,  Quality and Community Health, Helen DeVos Children's Hospital in Grand Rapids, Michigan

There are so many reasons for the obesity crisis in our kids that it’s hard to know where to start. But a recent study in the Archives of Pediatric and Adolescent Medicine is worth highlighting because it suggests a significant role for community pediatricians in at least one of those factors.

The study, by researchers from the University of Maryland and Johns Hopkins, was a cross-sectional analysis of a sample of low-income mothers and their toddlers. Researchers showed 281 mothers of toddlers (mean age 20 months, 11.9 to 31.9) silhouette pictures of children from 0 to the 100^th weight-for-length percentile, then asked them which picture looked most like their child and which picture they wanted their child to look like.

Just one-third of the mothers chose the silhouette that accurately depicted their child’s body size. Seventy-three percent of the mothers who were inaccurate had children who were overweight compared to 35% of the mothers who were accurate (P<0.001), making them 87% less likely to accurately assess their child’s size. In addition, 82% of mothers with overweight toddlers were satisfied with their child’s size compared to a third of mothers with healthy weight children.

Given that parental perceptions of their child’s weight can be a key factor in  the lifestyle  choices they make  for their family early in life, choices that that can contribute to child’s feeding behavior (such as exhorting children of a healthy weight to eat more), this study should raise our awareness of importance of parental perceptions of their child’s weight.

Plus, as the authors noted, it is hardly the first to document parental misperceptions of their child’s weight. However, it is the first to measure perceptions of parents of such young children. As you may know, there is good evidence that toddler weight predicts later weight.¹

However, let’s not only blame parents for misperceptions of weight; pediatricians do it, too.²

This study and others like it highlight the need for objective data on the size of very young children and documentation at every well-child visit, rather than relying only on weight or only on appearance. The American Academy of Pediatrics recommends precisely this—assessing BMI in children 2 and older, and weight-for-length in younger children.

The study also highlights the need to share this information with parents and engage them in conversations about healthy lifestyles and diet, even those with very young children. Such discussions could improve the accuracy of parental perceptions of their child’s weight, as well as help parents identify opportunities to support a healthy weight in their children.

How do you routinely assess children’s body size/weight in your practice?

Tom Peterson, MD, is executive director of Safety,  Quality and Community Health at Helen DeVos Children's Hospital in Grand Rapids, Michigan

1. Reilly JJ, Armstrong J, Dorosty AR, et al. Early life risk factors for obesity in childhood: cohort study. BMJ. 2005;330(7504):1357.

2. O'Brien SH, Holubkov R, Reis EC. Identification, evaluation, and management of obesity in an academic primary care center. Pediatrics. 2004;114(2):e154-159.