There May Be Health Benefits to Having a Younger Sibling, Study Finds

When you’re a kid, having a younger brother or sister can be a mixed bag. But whether you saw your kid sibling as a best friend or annoying nuisance, whether you loved having someone to play with or hated sharing your toys, it turns out there may be tangible health benefits to having a younger sibling.

According to a study led by the University of Michigan which will be published in Pediatrics next month, becoming an older sibling before first grade may lower the risk of becoming obese. The study, which compared the body mass indexes (BMIs) of 697 children across the United States, found that the birth of a sibling between the ages of two and four was associated with a healthier BMI. Children without a sibling, meanwhile, were close to three times more likely to be obese by the first grade. 

Researchers are not yet sure why the connection between younger siblings and weight exists. At the moment, they believe the birth of a second sibling may change the way parents feed their kids, or that having a sibling causes children to lead more active lives. Researchers believe that the simple presence of a younger sibling may motivate kids to spend less time involved in solitary, sedentary activities like television watching, and more time in so-called "active play."

The study was inspired, in part, by the desire to solve the mounting childhood obesity problem in America. “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,” said researcher Julie Lumeng. “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.”