Although many children might use terms like “annoying” and “aggravating” to describe their younger brothers and sisters (complete with the dramatic eye roll), a new study suggests younger siblings may help their older siblings achieve better health by staving off obesity.

Published in the journal Pediatrics, the study by University of Michigan researchers is the first to look at how children’s body mass index (BMI) changes with the arrival of a younger sibling.

“There are so many benefits to younger siblings,” Kelley Kitley, a psychotherapist in Chicago, Illinois, told LifeZette. “These findings make sense, since the activity level for the older child is naturally influenced by the increased household activity of a younger brother or sister.”

The researchers studied 697 children from birth, from 10 different U.S. locations, and assessed their “sibship” every three months — then classified them accordingly, Medical News Daily noted. The researcheres also measured the children’s BMI at 15, 24, 36 and 54 months, as well as in the first grade.

The findings? A little brother or sister doesn’t just provide a best buddy for building forts and running around with; the younger sibling also significantly lowers a child’s risk of obesity by the time that older child enters elementary school. Children in the study who did not have a sibling were almost three times more likely to be obese by the time they reached first grade.

[lz_ndn video =29617914]

The changes a family undergoes when another child comes along may be threefold, the researchers theorized. A child’s diet may change when a new sibling arrives, for starters. Parents of only children can sometimes be controlling or hyper-focused on what their kid eats, which can potentially lead to bad eating habits, Reuters reported.

Children may be more active when they have a sibling, too, spending less time in front of a television or iPad. Additionally, older children often assume a caregiver role, becoming more active as they play and nurture.

[lz_bulleted_list title=”2011-2012 Childhood Obesity Facts” source=””]17% of kids ages 2-19 are obese.|8.4% of kids ages 2-5 are obese|20.5% of kids ages 12-19 are obese.|2% of young children are severely obese.|5% of kids ages 6-11 are severely obese.|6.5% of kids ages 12-19 are severely obese.[/lz_bulleted_list]

“Childhood obesity rates continue to be a great cause of concern,” lead researcher Dr. Julie Lumeng told Medical News Today of the findings. “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. Better understanding of the potential connection between a sibling and weight may help health providers and families create new strategies for helping children grow up healthy.”

Who do you think would win the Presidency?

By completing the poll, you agree to receive emails from LifeZette, occasional offers from our partners and that you've read and agree to our privacy policy and legal statement.

The childhood obesity rate is climbing far too rapidly in the U.S.

An estimated 41 million children under 5 years old are either obese or overweight as of 2014, according to the World Health Organization — and the obesity epidemic is hitting developing nations especially hard.

The total number of obese young children in countries in Asia and Africa now outnumber those in such wealthier nations as the U.S., according to a recent report by the Commission for Ending Childhood Obesity.

[lz_related_box id=”72407″]

“Obesity ranks up there as one of the biggest issues, and it is preventable,” Miriam Nelson, director of the John Hancock Research Center on Physical Activity, Nutrition, and Obesity Prevention at Tufts University, told “You don’t necessarily want to pit one disease against another — there’s still major concerns about tuberculosis and HIV in many nations. But obesity will be an enormous burden on these children as they get older.”

Few parents would want to have another child just to curb their eldest’s obesity risk, but they can enjoy that possible benefit along with the many others that siblings bring.

“Siblings give so much to each other — the development of empathy, the ability to share the attentions of others,” said Kitley. “They will learn in the real world that it is sometimes hard to get another’s undivided attention, and siblings teach each other every day how to handle that.”

What of the only child, who can’t benefit from the presence of brothers and sisters?

“There are many only children out there, and benefits can be accomplished in other ways,” Kitley noted. “Try to re-create that system for the only child through playdates. Give them plenty of social outlets — and have an open-door policy for other children your child becomes friendly with.”