Children who welcome a younger brother or sister between age 2 and 5 are less likely to be obese than their peers and children who did not have a sibling by the time they reached first grade were 3 times as likely to be obese, a new study reports.
The study, published in Pediatrics, tracked 697 children across 10 sites in the United States at the time of birth, checking every 3 months to see if a new sibling had arrived in the household. Weight status and BMI were checked at 15 months, 24 months, 36 months, 54 months, and again in first grade. The researchers classified children based on the timing of their sibling’s birth and examined the association of the birth of a sibling with subsequent BMIz trajectory.
Only 5% of those who welcomed a younger sibling between age 3 and 4 were obese in the first grade. By contrast, 13% of those who did not have a younger sibling by first grade were obese.
Limitations of the study include the lack of objectively measured birth weights and information on events such a divorce, move, or job loss in the family – all of which can influence the odds that children might become obese – the authors note.