Is Obesity Contagious?

I recently saw a shocking documentary called “Globesity: Fat's New Frontier,” (ref 1) which shows that by 2030 more than one billion people worldwide will fall into the ‘obese’ category - a person is classed as 'obese' if they have a Body Mass Index of more than 30 (Kg=m2). The primary causes of these statistics are what we know: over-eating processed foods, lack of exercise, stress, environmental toxins, imbalances in key biological functions, and so on.

However, experts are becoming aware of another key cause, which is often ignored: the role that our social connections have on our health and happiness.

Indeed, it has been argued, as well as empirically proven, that that obesity may be "contagious" – it is a social disease which requires, at least partly, a social cure. Let’s see how.

How our social connections influence our health and obesity

Key empirical research was conducted by Harvard researchers (ref 2) using the Framingham data. They found 5,124 friends with 53,228 connections from 1971 to 2003. Their results were striking, showing how obesity appears to break out in social clusters:

  • People are 57% more likely to be obese if they had a friend who became obese.
  • People are 20% more likely to be overweight if their friend’s friend is overweight, and 10% more likely to become overweight if the friend of a friend of a friend became overweight.
  • Even more striking is what the researchers call ”directionality” - If John thought that Steve was his best friend and John gained weight, Steve would gain weight too. But if John didn’t think Steve was his best friend (just a friend), John was less likely to gain weight if Steve gained weight.

What we are seeing is that people within three degrees of separation from us shape our behaviour, maybe even if we have never met them! And, critically, the more a person feels connected to someone else the more his or her behaviours affect them. 

The researcher’s conclusion was: “Network phenomena appear to be relevant to the biologic and behavioral trait of obesity, and obesity appears to spread through social ties. These findings have implications for clinical and public health interventions.”

Indeed, look at what Microclinic International (ref 3) have achieved. Their motto is “Social networks and healthy behaviour = Contagious health”.  Their premise is that healthy and unhealthy behaviours are transmittable across social networks, so they work in and educate small groups to address both non-infectious and infectious disease epidemics such as diabetes and HIV/AIDS.

To date, they have established and evaluated over 1,500 microclinics across four continents. As an example, Bell County, Kentucky has some of the highest rates of obesity and type 2 diabetes in the country. After the 40 weeks pilot program, 95% of the participants had dramatically improved blood pressure, cholesterol, blood sugar, waist circumference and weight (BMI).

What are the Implications of these social connections?

These studies and evidence helped me to understand that our approach to addressing the 'epidemics' of obesity, diabetes and chronic disease may be backwards!

That’s because much of Conventional medicine focuses on the individual as if they had no social context. So ‘personal responsibility’ and ‘self-control/restraint’ are highly recommended.

But how can that be the whole story if you are more likely to gain weight if the friend of a friend gains weight?

Perhaps, we need to rethink our approach to obesity and chronic disease? So, the 'patient' may not be a person but the community, a social network of people who influence each other.

Think of the power of this approach. 

Most of us are linked in some way to many others, all of whom we can theoretically make healthier and happier by our behaviour. How we act, what we eat, if we gain or lose weight will influence the behaviour of many others, most of whom we don’t even know. 

I agree with the Harvard researchers and members of the microclinics that the way we will change our health and happiness is not only though the usual dietary, exercise etc. interventions. 

Rather, we also need to find fun and focused ways to get healthy together. Think of it as “friend power” rather than will power. Or, as I heard on the radio: “everybody needs a buddy.” 

What do you think?  I’d love to hear your thoughts on this!


  1. The documentary Globesity: Fat's New Frontier and
  2. The Harvard study in the New England Journal of Medicine, “The Spread of Obesity in a Social Network over 32 Years “
  3. Microclinic International