Could a younger sibling be good for the older child's health? The new study suggests so.
Results of the study - led by Dr. Julie Lumeng from the University of Michigan - are published in the journal Pediatrics.
Previous research has not been so kind to siblings. One study suggested infants are more likely to catch whooping cough from their siblings than from their mothers.
And another study declared that firstborn children have higher IQs than their younger siblings.
Dr. Lumeng and colleagues say previous research has already suggested that the structure of a family could influence weight, but theirs is the first to look at how children's body mass index (BMI) changes with the birth of a younger sibling.
For their research, the team recruited 697 children at the time of birth across 10 sites in the US and then assessed "sibship" every 3 months. The children were classified based on the timing of their sibling's birth.
Additionally, the researchers measured the children to assess BMI at 15, 24, 36 and 54 months, and in the first grade.
Children without sibling three times more likely to be obese in first grade
Overall, the findings revealed that becoming a big brother or sister before first grade lowered a child's risk of becoming obese.
In detail, the birth of a sibling when the first child was between 2-4 years of age was linked with a healthier BMI by first grade.
And children who did not have a sibling were almost three times more likely to be obese by the time they were in first grade.
Dr. Lumeng says that although the research associated the birth of a younger sibling with a lower risk of being overweight, they "have very little information about how the birth of a sibling may shape obesity risk during childhood."
She and her team theorize that parents might change how they feed their child when another sibling is born. Because children's eating habits are mostly developed around 3 years of age, the researchers say changing their dietary habits could have a major impact.
Furthermore, children may be more active and spend less time in front of screens once a younger brother or sister is born. And another theory is that older children could assume a caregiver role when a younger sibling is born, involving more active play and movement.
Commenting on their study, Dr. Lumeng says:
"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 of the potential connection between a sibling and weight may help health providers and families create new strategies for helping children grow up healthy."
She adds that further research needs to be conducted on how the birth of a sibling could impact mealtime behaviors and physical activity.
Medical News Today recently reported that fitness and strength in youth predicts diabetes, regardless of weight.