Researchers have identified another population that links obesity to a person’s place of residence: military families. And they suspect a form of social contagiousness is to blame.

Each additional percentage point in the adult obesity rate in the county to which a family was assigned was associated with 5 percent increased odds the adults would be obese and 4 percent increased odds the family’s children would be obese. The associations were stronger the longer a family spent in a particular location and for families who lived off the military base and among the local population, Ashlesha Datar, PhD, and Nancy Nicosia, PhD, wrote in JAMA Pediatrics.

Previous studies have tied locational obesity trends to “built environments.” For example, a study published in December 2017 found people living closer to gyms—and away from fast-food restaurants—were more likely to have lower waist circumference, body fat and body mass index (BMI).

But Datar and Nicosia attempted to adjust for those factors in their analysis, suggesting social factors are also at play. Social contagion may manifest itself through mirroring other people or changing perceptions about appropriate weight status based on the characteristics of individuals in the surrounding community, they wrote.

The researchers recruited families from 12 military installations across the United States. A total of 1,314 adults and 1,111 children were included in the study, which had similar obesity rates to that reported in the general U.S. population.

“We study military families because service members are routinely assigned to installations based on the needs of the military, thereby providing plausibly exogenous variation in their exposure to communities with varying rates of obesity,” the authors wrote. “The reason and duration of exposure is outside of the control of individuals (with rare exceptions), offering a unique opportunity to study whether living in communities with higher rates of obesity can make individuals more likely to become obese themselves.”

Although their results suggest a social component to the development of obesity, Datar and Nicosia were unable to identify or examine specific factors.

In an accompanying editorial, Leonard H. Epstein, PhD, and Xiaozhong Wen, MD, PhD—both with the department of pediatrics at Jacobs School of Medicine and Biomedical Sciences, University of Buffalo—said the study would have been stronger if individual obesity status was known prior to families’ moves and what the obesity rates were in their previous counties of residence.

“With this information, the authors could have established whether an increase in obesity was owing to social contagion if they moved from an area with a low prevalence of obesity to one with a greater prevalence of obesity, or a reduction in obesity if they moved to an area with a lower prevalence of obesity,” they wrote.

The editorialists also said it is important to remember children are more susceptible to developing obesity if their family members are obese than if their peers and other adults in the community are overweight. They recommended family-based treatment approaches, where changing a parent’s habits may also positively impact a child’s behaviors.

“The idea of obesity being contagious provides a very useful analogy for pediatricians to recognize the association of the social environment with obesity (through social networks and/or social norms),” Epstein and Wen wrote. “It provides a stimulus to action to learn how to deactivate the ‘virus,’ preventing transmission to future generations.”