More evidence for ‘social contagion’ in obesity
medwireNews: Researchers have found that the bodyweights of family members of military personnel tend to change to match what is predominant in their area of posting.
The study from Ashlesha Datar (University of Southern California, Los Angeles, USA) and Nancy Nicosia (RAND Corporation, Boston, Massachusetts, USA) involved 1519 military families; one parent and one child from each of these were asked to complete an online survey, resulting in responses from 1314 parents and 1111 children. Three-quarters of the parents were overweight or obese, as were more than a quarter of the children.
The families were assigned to reside in US counties with obesity rates ranging from 21% in El Paso County, Colorado, to 38% in Vernon County, Louisiana. The fact that they were assigned to these places, without having a say, gets around the problem of families opting to move to areas in which they feel comfortable, stress the researchers.
Each 1% increase in the obesity rate for the assigned county was associated with a significant 0.08 kg/m2 increase in the BMI of parents and a 0.01 kg/m2 increase in that of the children, the team reports in JAMA Pediatrics.
There was also a significantly increased risk for parents becoming obese and for children becoming overweight or obese, and this association remained significant in a subsample of 458 children who had anthropometric measurements made by a healthcare provider available.
The association between county and family overweight was stronger in families who had been in their posting for longer than 2 years than in those with shorter stays, and in families who lived away from the military base than in those living at the base, supporting a direct effect of their social environment.
These associations persisted after accounting for built environment factors, such as the proportion of people living near a park or recreational facility, and local walkability. “While this study cannot definitively rule out the role of shared environments with the available measures, these findings suggest that other mechanisms may be at work,” observe Datar and Nicosia.
In a linked editorial, Leonard Epstein and Xiaozhong Wen, both from University at Buffalo in New York, USA, also highlight the difficulty of fully accounting for the effects of shared obesogenic environments.
In addition, they caution that the authors were able to account for the families’ geographic location but not their specific social interactions, which was the critical factor in a previous analysis of the Framingham Heart Study cohort (ie, the bodyweight of socially close friends had a greater effect than that of physically close neighbors).
Nevertheless, the editorialists describe the study as “unique” and say that the “idea that obesity can be contagious” is relevant to public health policy as well as to medical practice.
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