Siblings' Excess Weight Increases Risk of Obesity in Families

Having obese brothers and sisters can greatly increase the risk of obesity as a child--even more so than having obese parents. However, a recent study, published in the American Journal of Preventive Medicine, also found that numerous factors increase the risk of this health issue. 

For the study, researchers surveyed 10,244 American households to determine how the number of children affected the likelihood of childhood obesity. Findings revealed that in a single child household, a child might be 2.2 times more likely to be obese if a parent was also obese. However, families with two children showed a stronger link to sibling obesity than parental obesity.

"For youngest boys in two-child families, obesity is 11.4 times more likely with a male older sibling," the study authors said, in a news release. "If that younger boy's elder sibling is a girl, the boy is 6.6 times more likely to be obese. In two-child families, youngest-girl obesity is 8.6 times more likely with a female older sibling and is not significantly more likely if the older sibling is male. Thus, for younger children, there is a discernible gender correlation in sibling obesity status: having an obese elder same-gender sibling is associated with an increased likelihood of the younger child being obese."

The study results extend findings that obesity is often related between siblings to similarities found between parents. Furthermore, the study results also highlight just how important exercise and a healthy diet are for keeping fit.

"Younger siblings with more vigorous physical activity are significantly less likely to be obese, though having an elder sibling who is extremely active is associated with a higher risk of younger-sibling obesity," added lead investigator Mark C. Pachucki, PhD, Mongan Institute for Health Policy, Massachusetts General Hospital, Boston, Mass.  "In seeking to reduce the prevalence of childhood obesity, it may be productive to consider prevention and treatment models that meaningfully recognize siblings as interconnected."