Overweight siblings ‘revealing indicator of childhood obesity’

8 July 2014

It is widely know that children of overweight parents are themselves more likely to be obese, but new research suggests that different family associations could affect a person’s risk of developing the condition.

A collaborative study from Massachusetts General Hospital, Cornell University and Duke University found a link between having an obese sibling and a child’s risk of being overweight, as well as a correlation between the parent’s weight and their offspring’s.

The research team surveyed 10,244 households and discovered that the likelihood of childhood obesity fluctuates depending on the number of children in the family, as well as their genders.

According to the results, in a single child household, a youngster is 2.2 times more likely to be obese if the parent also has the condition. In families with two children, the findings suggest there is a stronger relationship between sibling obesity than parental.

Older children in a family with two youngsters with an obese parent are 2.3 times more likely to develop the condition. This number jumps to 5.4  for those that have overweight younger siblings. If a child is the younger brother or sister, parental obesity is not a risk factor, but having an overweight sibling is linked to a 5.6-fold higher risk.

Dr Mark C Pachucki, from Massachusetts General Hospital and lead author of the study, believes the family environment exerts a strong influence over a child’s health. He added that previous research has shed light on the connections between parent and offspring obesity and others have found a link between obesity and siblings.

He said: “Our study extends these findings by integrating data on both parent-child, and sibling relationships. We found that obesity status of a younger child's older sibling is more strongly associated with a child's obesity than is the parent's obesity status.”

"This association is independent of a host of socioeconomic and demographic attributes, health behaviors, and overall health status."

The findings also uncovered a link between gender and obesity risk, as in one-child homes, girls were less likely to be overweight compared to their male counterparts. In families with two children, younger children are susceptible to the influence of older siblings, especially if they are of the same sex.

According to the study’s authors, the youngest boys in a two-child household are 11.4 times more likely to become obese if they have an older male sibling. If the boy has an older sister then he is 6.6 times more likely to develop the condition. Conversely, in the same household, the youngest girl has an 8.6-fold higher risk of being obese with a female older sibling and if she has an older brother, there is no notable increase in risk.

“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," wrote the authors.

Obviously, exercise and diet both play important roles in the prevention of obesity. Researchers discovered that children without siblings were less likely to be physically active and more likely to eat junk food compared to their counterparts with brothers and sisters.  

Strangely, the results of the study revealed that having a highly active older sibling raised the risk of obesity for younger children. The authors believe the new study offers key data that will be beneficial in the fight against childhood obesity, but have stressed that more ‘within-family’ research is needed.

Posted by Jeanette Royston

Health News is provided by Adfero in collaboration with Spire Healthcare. Please note that all copy above is ©Adfero Ltd. and does not reflect views or opinions of Spire Healthcare unless explicitly stated. Additional comments on the page from individual Spire consultants do not necessarily reflect the views or opinions of other consultants or Spire Healthcare.

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