Study Finds Exposure to Areas With High Overweight/Obesity Rates Affects BMI

An individual’s body mass index (BMI) can increase when exposed to counties with a higher prevalence of obesity, according to a study published in JAMA Pediatrics.

Certain areas in the United States have been associated with higher levels of overweight and obesity in adults and children. In the past, researchers have considered weight gain to be a social contagion—as more people become overweight or obese in a community, the likelihood of other people gaining weight in the same environment increases. If overweight/obesity in individuals is, in fact, a social contagion, then public health policy can easily intervene within communities to promote healthy eating and exercise.

The researchers sought to find out if exposure to communities with higher rates of overweight and obese members would increase the BMI of individual residents. In order to eliminate the role self-selection plays in choosing an area to life, military families were chosen as the best participants for the study since the government assigns the location of residency. The study included 38 installations across 35 counties.

The study used already collected data from the Military Teenagers’ Environments, Exercise, and Nutrition Study. The adult obesity rate in the military member’s assigned county was used to measure exposure.

From the 1519 participating families, 1 parent and 1 child were included in the study from November 2016 to October 2017. The outcomes for adults were BMI, overweight/obesity (BMI, > 25) and obesity (BMI, > 30). BMI z score, overweight/obesity (BMI percentile for age and sex, > 85), and obesity (BMI percentile for age and sex, > 95) were measured outcomes for children.

Self-reports from parents and children recording height and weight determined the outcomes for the participants. A total of 1314 adults and 1111 children were included in the study.

The data show that a 1% higher county obesity rate was associated with a higher BMI and increased chance of obesity in parents. In children, a higher BMI z score and greater odds of overweight/obesity were also associated with a higher county obesity rate.

Limitations acknowledged by the authors included the focus on geography and not the network-based interactions associated with weight gain and the BMI self-reports from parents that could be miscalculated.

“Exposure to counties with a higher prevalence of obesity was associated with higher BMI, overweight, and/or obesity in parents and children,” the authors concluded. “There was no evidence to support self-selection or shared environment as explanations for this association, which may suggest the presence of social contagion in obesity.”

References

Datar A, Nicosia N. 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. [published online January 22, 2018]. JAMA Pediatr. doi: 10.1001/jamapediatrics.2017.4882.