New research on the social network effects of obesity was recently reported in the Guardian UK:

Children at schools where older students are obese or otherwise overweight are significantly more likely to suffer weight problems themselves, researchers report.

For each one per cent increase in the prevalence of obese students aged 16 to 18 years, the odds of a student at 14 to 16 years old attending that school also being overweight increased significantly.

“It was the one risk factor that held true across every school we looked at,” said Dr Scott Leatherdale, the chair of research at Cancer Care Ontario and lead investigator with the School Health Action, Planning and Evaluation System.

Commenting on the obesity connection between older and younger students, Leatherdale says:

It could be that younger students look up to older students, and so emulate their sedentary behaviour and bad eating habits and do not judge the older children’s body shape.  Or it could be that the school doesn’t encourage enough physical activity among its students, and the older students’ weight issues are an indication of that.

Sociologist Steve Fuller at Warwick University concurs with his assessment:

Obesity is one phenomenon that medical sociologists have nominated as an ‘epidemic’ that is transmitted by copying the behaviour of peers.  Certain connections between overeating and social activities become contagious. Young people gather together in more stationary modes than in the past: in front of computers and video games rather than sports.

The reason it’s called an ‘epidemic’ is because the pattern is reinforced by regular contact, so that if one is not in regular contact with the pattern, one doesn’t spontaneously do it The idea is that you overcome obesity by breaking up the networks where it’s transmitted.