Obesity, like the chicken pox, can be contagious
U.S. military members serve their country in myriad ways. That includes helping researchers figure out whether obesity is a contagious disease.
A new study involving thousands of military families suggests the answer is yes.
The idea that fatness can spread like chickenpox or the flu may sound crazy. But how else do you explain the fact that families assigned to army bases in communities with higher rates of obesity were more likely to be overweight or obese compared with families sent to bases where excess pounds were less common?
That finding, published this week in the journal JAMA Pediatrics, offers the first quasi-experimental evidence to support the theory that obesity spreads through social contagion.
The theory is based on observations by Dr. Nicholas Christakis of Yale and James Fowler of UC San Diego, who found that various kinds of behaviours appear to propagate through social networks. They mapped out friend and family relationships among three generations who participated in a long-running heart study and found that things such as smoking, happiness and divorce seemed to spread as if they were contagious.
Obesity was one of the very first social contagions they identified. An ideal experiment would be to find people who are not obese and randomly assign them to social networks with varying degrees of obesity. If it were contagious, you would expect that people in networks with more obesity would gain more weight than people in networks with less obesity.
A pair of economists realized the military had done something similar by assigning servicemen and women to live on army bases across the U.S.
Ashlesha Datar of USC and Nancy Nicosia of the Rand Corp. gathered data from a study known as MTEENS.
The kids who were part of this study had a parent assigned to one of 12 bases. The obesity rates in those communities ranged from 21 per cent in Colorado’s El Paso County to 38 per cent in Louisiana’s Vernon Parish.
The data that Datar and Nicosia pulled showed that about a quarter of the teens and 75 per cent of the adults (most active-duty personnel) were either overweight or obese, based on their body mass index.
After adjusting for factors such as age, sex, education, income and military rank, they found members of military families were more likely to be overweight or obese if they had been deployed to a county where obesity was more of a norm.