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Nikolas Christakis (a professor at Harvard Medical School) and James Fowler (from the University of California, San Diego) have found that friends affect both our weight and our happiness.

1. Weight
In a study published in the July 26 issue of the New England Journal of Medicine Christakis and Fowler report that if one person becomes obese, those closely connected to them have a greater chance of becoming obese themselves. (The researchers analyzed data over a period of 32 years for 12,067 adults, who underwent repeated medical assessments as part of the Framingham Heart Study.)

“It’s not that obese or non-obese people simply find other similar people to hang out with . . . Rather, there is a direct, causal relationship.” said Christakis.

The greatest effect is among friends.

Among siblings, if one becomes obese, the likelihood for the other to become obese increases 40 percent; among spouses, 37 percent. If a person you consider a friend becomes obese, your own chances of becoming obese go up 57 percent. Among mutual friends, the effect is even stronger, with chances increasing 171 percent. (There was no effect among neighbors, unless they were also friends.)

Further analysis also suggested that people’s influence on each other’s obesity status could not be put down just to similarities in lifestyle and environment

“When we looked at the effect of distance, we found that your friend who’s 500 miles away has just as much impact on your obesity as [one] next door,” said Fowler.

Fowler also points out that it is not just about obesity. He said,

“It’s important to remember, that we’ve not only shown that obesity is contagious but that thinness is contagious.”

2. Happiness
In a study published in the British Medical Journal the same authors looked at the affect that social networks had on happiness. (James H Fowler, Nicholas A Christakis. Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study. British Medical Journal, December 4, 2008)

“We’ve found that your emotional state may depend on the emotional experiences of people you don’t even know, who are two to three degrees removed from you,” says Christakis.

The researchers found that when an individual becomes happy, a friend living within a mile experiences a 25 percent increased chance of becoming happy. A co-resident spouse experiences an 8 percent increased chance, siblings living within one mile have a 14 percent increased chance, and for next door neighbors, 34 percent. A friend of that friend experiences a nearly 10 percent chance of increased happiness, and a friend of *that* friend has a 5.6 percent increased chance—a three-degree cascade.
In this case being geographically closer does make a difference. The closer a friend lives to you, the stronger the emotional contagion. In addition, the happiness effect appears to wear off after roughly one year.

Examination of this dataset shows that having $5,000 extra increased a person’s chances of becoming happier by about 2 percent. But, as Fowler notes, “Someone you don’t know and have never met—the friend of a friend of a friend—can have a greater influence than hundreds of bills in your pocket.”

3. Long Life
This study (BMJ Specialty Journals (2005, June 16)) aimed to assess how economic, social, behavioural and environmental factors affected the health and wellbeing of people aged 70 and upwards. In total, almost 1500 people were asked how much personal and phone contact they had with their various social networks, including children, relatives, friends, and confidants. Survival was monitored over 10 years.

Close contact with children and relatives had little impact on survival rates over the 10 years. But a strong network of friends and confidants significantly improved the chances of survival over that period. Those with the strongest network of friends and confidants lived longer than those with the fewest friends/confidants.

The beneficial effects on survival persisted across the decade, irrespective of other profound changes in individuals’ lives, including the death of a spouse or close family members, and the relocation of friends to other parts of the country.

4. Happiness Lengthens Life
Finally, for this post, not only do friends influence your happiness and your longevity, happiness increases your longevity too.

An analysis of thirty studies has concluded that while happiness does not heal, it does protect against falling ill. As a result, happy people live longer. The size of the effect on longevity is comparable to that of smoking or not.

One of the mechanisms behind that effect seems to be that chronic unhappiness causes stress, which on its turn reduces immune response. Another possible mechanism is that happiness adds to the chance of adopting a healthy life style.
(Veenhoven et al. Healthy happiness: effects of happiness on physical health and the consequences for preventive health care. Journal of Happiness Studies, 2008; 9 (3): 449)

For me the implications of these studies are huge. The take home message for us as individuals is:

  • make friends
  • being healthy will influence your friends to be healthy
  • Our friendships affect our weight, happiness and length of life. What’s more our happiness also increases our longevity.
  • you can help your friends to be happier – and if several people do this the effect can be self-reinforcing.

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6 Comments to “Wellbeing and Our Friends: happiness, health and long life.”

  1. Maudrey says:

    I have always noticed that my bestfriend (of some 20 years) and I always seemed to have similar things happening to us over the years. Our love lives always seemed to be mysteriously connected in that when everything was going well in my relationship, hers was blooming as well. But we also noticed that when her personal relationships were troubled, so were mine and vice versa. In our early 20s, we both gained weight on the same summer even if we didn’t spend that much time together. Interestingly enough, even our body clocks seemed to be synchronized as well. This has always baffled us and sometimes even freaked us out. So thanks for the enlightening post. This truly explains a lot. At least now, we can both strive to be happy so that we can both live longer.

  2. Evan says:

    Hi Maudrey,

    Welcome. These kind of things can seem a bit freaky can’t they. I have two friends who seem to have the same moods – even when they haven’t contacted each other. One rings the other, even after a few weeks and they are feeling the same.

    Thanks for your comment.

  3. I have heard that most of us are the average of our 20 closest friends and family members. This applies to everything from weight and fitness to income. It seems like one of the best things we can do to be happier and healthier is to seek out happy, healthy friends.

  4. Evan says:

    Hi Maria,

    I hadn’t heard this. It sounds right to me though.

    I’m interested in the potential it has for a few of us to influence each other in healthy ways. It’s got me thinking.

    Thanks for your comment.

  5. Lethoko Puiso says:

    i agree with studies found here. i did have knowledge about some, like happy people can live longer. i also found it intriguing that a friend of a friend can influence how i feel. of interest to know can be, this topic, does sex reduce streng after intercource?

  6. Evan says:

    Hi Lethoko, glad you liked the post. As to strength and sexuality – there are various practices in Eastern traditions to avoid ejaculation and so on, if this is the kind of thing you mean. These people don’t seem on the whole to live longer than Westerners who don’t practise these kinds of things. This is just my personal observation.

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