PhotoThe desire to give your first born a buddy to play with might factor into your decision to have another baby. But research shows there is another benefit to giving your child a younger sibling.

Children who become a big brother or sister before first grade may see a lower chance of becoming obese, according to a study led by the University of Michigan.

The study -- set to appear in the April issue of Pediatrics -- discovered a link between the birth of a sibling and a healthier BMI by first grade. This was especially true when the newly crowned big brother or sister was between the ages of two and four at the time of their sibling’s arrival.

According to senior author Julie Lumeng, M.D., a developmental and behavioral pediatrician at U-M’s C.S. Mott Children’s Hospital, this study is the first to track increases in BMI following the arrival of a baby brother or sister.

The research, she explains, suggests that younger siblings -- compared with older or no siblings -- play a role in lowering a child's risk of being overweight. As to why this association might be, the authors believe changes in eating habits and activity levels could be to thank.

Changes habits

After a new sibling is born, parents might change the way they feed their child. The timing of this change -- around age three, when children are developing long-lasting eating habits -- might alter the way they eat for years to come.

The presence of a busy little brother or sister might also translate to less screen time for older siblings. (After all, who needs Dora when there’s an exciting new buddy in the house?) The researchers say this increase in “active play” could also help define the association between younger siblings and a healthier BMI.

While further study is needed to examine the effect of having a sibling on mealtime behaviors and physical activity, Lumeng says studies like these can help increase our understanding of how to fight childhood obesity.

“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 Lumeng, adding that understanding such associations can help families and doctors create new strategies for helping children grow up healthy.

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