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That pesky kid brother or sister who broke your stuff and got you in trouble all the time may have actually done you a favor: A new study suggests that younger siblings might be good for your health.

That’s because that by first grade, kids with younger siblings are much less likely than others to be obese.

Children who didn’t welcome a baby brother or sister into the family before first grade had almost triple the odds of obesity compared with kids who experienced the birth of a sibling when they were around 3 to 4 years old, the study found.

The study doesn’t prove that being an only child will cause obesity or show how adding a baby to a family might help older kids maintain a healthy weight.

But the results suggest that parents may make lifestyle changes after expanding the family that could be beneficial even before another baby arrives, said senior study author Julie Lumeng, a pediatrics and public health researcher at the University of Michigan and C.S. Mott Children’s Hospital in Ann Arbor.

“It is possible that when there is a younger sibling in the family, a child might become more active — for example, running around more with their toddler sibling,” Lumeng said by email.

“Maybe families are more likely to take the kids to the park when there is a younger sibling, or maybe the child is less likely to be sedentary, watching TV, when there is a younger sibling to engage them in more active pretend play,” she added.

Mealtimes might also be different with a second kid at the table.

At tines, parents of only children can be controlling or hyper-focused about what their kid eats, which can lead to bad eating habits, some previous research suggests.

“When parents use restrictive (e.g. keep food from children) or pressure-to-eat feeding practices (e.g. try to get kids to eat more food), children have an increased risk of being overweight,” Jerica Berge, a researcher at the University of Minnesota, said by email.

“When a new child is introduced, parents may relax their preoccupation with the older child’s eating behaviors, allowing the older child to respond to their own satiety cues and self-regulate their eating,” said Berge, who wasn’t involved in the new study. “This self-regulation may lead to a healthier weight trajectory for the child with a sibling compared to a child without a sibling.”

For their study, Lumeng and colleagues followed 697 U.S. children from birth through age 6.

At 6 years old, the kids without siblings were more likely to have higher-than-average weight for their height than peers who did have a younger brother or sister, the researchers reported in the journal Pediatrics.

Limitations of the study, the authors noted, included the lack of objectively measured birth weights and information on events such as a divorce, a move or a job loss in the family — all of which can influence the odds that children become obese.

Other factors that can affect child obesity include parental weight, maternal weight gain or diabetes, breast-feeding, early introduction of solid food, family meals, bedtime routines, TV time and physical activity, said Sandra Hassink of the American Academy of Pediatrics Institute for a Healthy Childhood Weight, who was not involved in the study.

“This is a very interesting study that makes an observation but there is not enough information yet to understand why children without siblings would be heavier,” Hassink said by email.

— Reuters