A new study suggests that kids who grow up with younger siblings are significantly less likely to become obese.
Researchers at the University of Michigan found that becoming an older brother or sister before first grade significantly lowers a child's risk of becoming overweight. In fact, children who don't have siblings were nearly three times more likely to become obese by first grade.
The research team looked at data from 697 children across the U.S. and found that children who experienced a birth of a younger sibling between the ages of 2 and 4 had the healthiest body mass index by first grade.
"Children whose sibling was born when they were 24 to 36 months or 36 to 54 months old, compared with children who did not experience the birth of a sibling by first grade, had a lower subsequent BMIz trajectory and a significantly lower BMIz at first grade. Children who did not experience the birth of a sibling by the time they were in first grade had 2.94 greater odds of obesity at first grade compared with children who experienced the birth of a sibling when they were between 36 to 54 months old," the researchers wrote in the study.
Senior author Julie Lumeng, M.D., a developmental and behavioral pediatrician at University of Michigan's C.S. Mott Children's Hospital, and her team said that the latest findings are important because they are the first to suggest a link between siblings and weight.
"Research suggests that having younger siblings - compared with having older or no siblings - is associated with a lower risk of being overweight. However, we have very little information about how the birth of a sibling may shape obesity risk during childhood," Lumeng said in a university release. "This study is believed to be the first to track subsequent increases in body mass index after a child becomes a big brother or sister."
So how does having a younger sibling lower a child's risk of becoming obese? Lumeng and her team believe that children with younger siblings are more likely to be physically active because they have someone to play with. Parents are also more likely to change the way they feed their child once a sibling is born, the researchers explained.
"We need to further study how having a sibling may impact even subtle changes such as mealtime behaviors and physical activity," Lumeng concluded. "Childhood obesity rates continue to be a great cause of concern. If the birth of a sibling changes behaviors within a family in ways that protect against obesity, these may be patterns other families can try to create in their own homes. Better understanding the potential connection between a sibling and weight may help health providers and families create new strategies for helping children grow up healthy."
The findings are published in the March 2016 issue of the journal Pediatrics.
