Becoming an elder brother or sister before pre-school days can lower a child's risk of becoming obese, researchers suggest, adding that children who didn't have a sibling are three times more likely to become obese by the first grade.
The birth of a sibling by the time a child reaches the first grade or when the child is between two and four years can help the kid maintain a healthier body mass index (BMI).
"Having younger siblings -- compared with having older or no siblings -- is associated with a lower risk of being overweight," said senior author Julie Lumeng, paediatrician at University Of Michigan.
However, how the birth of a sibling can shape risk of obesity during childhood is unclear yet.
Children may possibly engage in more "active play" or less sedentary time in front of screens once a younger sibling is born, contributing to healthier BMIs.
Also, parents may change the way they feed their child once a new sibling is born and the changing dietary habits may have a significant impact on their BMI.
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Childhood obesity rates continue to be a great cause of concern. If the birth of sibling changes behaviours 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 authors suggested.
The study that included 697 children across the US is forthcoming in the journal Pediatrics.