body mass index

Obesity is on the rise as a serious global chronic disease concern and researchers have started to gather evidence showing that obesity can be spread socially. American researchers studied military families to determine whether body mass index is socially contagious and published their results in JAMA Pediatrics.

An emerging topic in health research has been the idea of the health of those in a community being connected. Multiple research studies shave demonstrated that people in social networks tend to have health-related attributes or conditions such as obesity in common; importantly, some have argued that obesity tends to be present in members of the same social networks because of a phenomenon called social contagion. Social contagion implies that obesity can be spread socially by members of a social group influencing one another’s behavior, thus simply being in an obese social network could increase the likelihood of having a higher body mass index (BMI).

Though this area of research has become popular over the last decade, critics have two main issues with the idea of social contagion. Firstly, some critics argue that the tendency for most individuals in certain social groups to be obese could simply be due to living in shared environments or homophily (which refers people preferring to socialize with people like themselves). To test whether social contagion or shared environments could explain obesity rates in social networks, a group of American researchers recruited a sample of army service members and their children. The researchers measured the average body mass index of the counties that the army service member was living in, then they measured the weight and height of each parent and child using self-reports. They recently reported their results in JAMA Pediatrics.

Social Contagion Explains Obesity Rates

The researchers found that the military families who lived in counties with high obesity rates were more likely to be overweight or obese in comparison to military families who lived in counties with lower obesity rates. This strong relationship persisted even when researchers continued their statistical tests and considered military families who lived in shared environments.

The use of military families was an interesting natural experiment because families could not choose to live in a certain area, so this factor was an unlikely explanation for the positive relationship mentioned above. No common characteristics among military families were identified as a possible explanation for obesity patterns documented in counties with existing high or low obesity rates. Seeing as self-selection into social groups and shared environments could not explain their findings, the researchers suspect that other causal factors may be at work.

The research demonstrated that the obesity of the military personnel and their families tended to mirror the obesity rate of the community in which they lived. Social contagion appears to be the most likely explanation for these shared obesity rates. Further research is needed to understand whether overweight children underestimated their own weights or developed inappropriate understandings of a healthy weight due to a high body mass index being common among their parents.

Written by Melissa Booker

Reference: Datar, A., & Nicosia, N. (2018). Association of Exposure to Communities With Higher Ratios of Obesity with Increased Body Mass Index and Risk of Overweight and Obesity Among Parents and Children. JAMA Pediatrics, 90089. https://doi.org/10.1001/jamapediatrics.2017.4882

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