01 February 2018

Is obesity contagious?

The phenomenon of 'social contagion' suggests that if more people around you are obese, it increases your own chances of becoming obese.

We all know that colds and flu are contagious, but is it possible that we can also "catch" lifestyle diseases like obesity from other people? 

It seems that living in a neighbourhood with a high rate of obesity might raise the odds that you and your children will become plus-sized, too.

Children affected as well

That's according to a new study involving more than 1 500 US Army families. The researchers say their findings may help explain why high obesity rates in the United States tend to cluster in certain geographic areas.

This kind of problem is not exclusive to the US, and in South Africa excess body weight is an equally big problem. Not only adults are affected as 13% of children are overweight and obese – more than double the global average of 5%.

"Living in a community where obesity is more of the norm than not can influence what is socially acceptable in terms of eating and exercise behaviours and body size," explained study author Ashlesha Datar.

The findings were published online in the Journal of the American Medical Association.

A phenomenon called "social contagion" may be at work, she said, though the study did not prove a cause-and-effect link. (According to Oxford Reference social contagion is the spread of ideas, attitudes, or behaviour patterns in a group through imitation and conformity.)

Countries with higher obesity rates

The bottom line: "If more people around you are obese, then that may increase your own chances of becoming obese," said Datar, a senior economist at the University of Southern California Center for Economic and Social Research.

The researchers sifted through 2013–2014 data for about 1 300 parents and 1 100 children. The families were stationed at or near 38 military installations across the United States.

Datar wanted to see if families had higher odds for being overweight or obese when posted in counties with higher rates of obesity.

  • The team first reviewed body mass index (BMI) for family members. BMI is a measure of body fat based on height and weight.
  • They then assessed the "shared environment" in which service families lived, tallying up the number of grocery stores, sports and recreational facilities, etc.
  • The researchers also weighed each community's overall obesity rate. These ranged from 21% to 38%.

Datar said the analysis confirmed that "military families assigned to installations in counties with higher obesity rates were more likely to be overweight or obese than military families assigned to installations in counties with lower rates of obesity."

But the opposite also appears true: Relocating to a county with a lower obesity rate reduces a family's odds of plumping up.

Health, eating and exercise

Datar said the study found no evidence to suggest that "neighbourhood shared environments" – such as access to the same eating and exercise options – were driving obesity rates.

Lona Sandon is an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas.

"It is well known in the behaviour and psychology literature that those around us influence behaviours, values and beliefs," she said.

"That includes behaviours, values and beliefs related to health, eating and exercise," Prof Sandon added. "Social acceptability and norms have a lot to do with food and exercise behaviour choices, whether we are aware of it or not."

Prof Sandon's advice: "If you want to change your weight, eating and exercise habits, get new friends who are already eating healthier and exercising."

Image credit: iStock


Live healthier

Lifestyle »

E-cigarettes: Here are five things to know

E-cigarettes have become hugely popular in the past decade, but a rash of vaping-linked deaths and illnesses in the US is feeding caution about a product that's already banned in some places.

Allergy »

Ditch the itch: Researchers find new drug to fight hives

A new drug works by targeting an immune system antibody called immunoglobulin E, which is responsible for the allergic reaction that causes hives.