(HealthDay News) — A sibling may be a better predictor of a child’s obesity status than his or her parents, especially for same-gender siblings, according to a study published online July 7 in the American Journal of Preventive Medicine.

Mark C. Pachucki, PhD, from Massachusetts General Hospital in Boston, and colleagues conducted a national survey and identified 1,948 adults who had one or two children. The participants provided sociodemographic information, height and weight for adult and child, and information about physical activity and food environment.

In one-child households, the researchers found that it was 2.2 times more likely that the child would be obese if a parent was obese. In two-child households, having an obese younger sibling was more strongly associated with elder-child obesity (odds ratio [OR], 5.4) than a parent’s obesity status (OR, 2.3). Parent obesity status was no longer significant when an obese elder sibling was present and associated with younger-child obesity (OR, 5.6). Patterns between siblings of the same gender were stronger than between different genders, when examining within-family sibling obesity. Child physical activity was significantly associated with obesity status.

“Considering offspring composition and sibling gender may be beneficial in childhood obesity prevention and intervention,” the authors write.

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