A new study has revealed that having an obese sibling associated with more than double the obesity risk of an obese parent; risk even stronger among same-gender siblings.
The study led by an investigator at the Mongan Institute for Health Policy at Massachusetts General Hospital found that the risk associated with having an obese sibling is more than twice as great as that of having an obese parent, and that risk is even stronger among siblings of the same gender.
Mark Pachucki, PhD, of the Mongan Institute said that it's a well known that diet and physical activity are key determinants of obesity among both adults and children; and prior research has shown that parents have a direct impact on children's eating habits through shopping and preparing meals and on their exercise by encouraging and facilitating access to activities.
According to the study, in families with only one child, having an obese parent was associated with more than double the risk that the child would be obese, although that risk was reduced if high levels of physical activity were reported for the child.
However, it was found that in two-child families, having an obese sibling was associated with risk that was more than five times greater than if the sibling were not obese. While the impact of parental obesity on an older sibling was the same as on an only child - approximately doubling the risk - among younger siblings there was no association with parental obesity.
The researchers also found that if the two children in a family were of the same gender, an older sibling's obesity had an even stronger association with obesity in the younger sibling - 8.6 times greater for girls and 11.4 times greater for boys. Of other demographic, socioeconomic and behavioral factors analyzed - including the number of fast food meals consumed weekly - the only one that significantly changed the impact of a sibling's obesity was the level of physical activity.
The study was published online in the American Journal of Preventive Medicine.