Author: Joshua Payne
Editors: Ian Cho, Emily Yu
Artist: Tracy Xu
In the United States, the incidence of obesity has increased from 23% to 31%, and over 66% of adults are overweight. An increase in obesity has occurred among all socioeconomic groups; obesity cannot be explained solely by genetics. Attempts to explain the spread of obesity have come from many sources including legends and myths.
Both Western and Asian cultures have a fable warning against keeping bad company. In the West, Aesop’s fable describes an Ass and his Purchaser; in China, the story of Mother Meng’s Three Moves. Both make a similar point by showing how proximity affects behavior.
Modern sociology has quantified the positive and negative effects of a person’s friends on their behavior and attitude, especially regarding obesity. As the saying goes, "There’s always a shred of truth behind every myth.” Can we find scientific facts to support that myth?
The Framingham Heart Study is a seminal study of how friendships influence behavior, specifically eating habits and the resulting obesity. Dr. Nicholas A. Christakis studied the body mass index (BMI) of over 12,000 people over more than 30 years through three generations in Framingham, Massachusetts. The study aimed to determine whether weight gain in one participant was influenced by weight gain in another. The participants were all part of a densely interconnected social network in the same town so they were expected to influence one another. The study confirmed that changes in behavior are connected to the company you keep.
For example, Christakis observed that “a person's chances of becoming obese increased by 57%...if [they] had a friend who became obese.” The study also emphasizes the difference between genders; it shows that “persons of the same sex had relatively greater influence on each other than those of the opposite sex.” When friendships were between two male individuals, the chance of becoming obese to match the friend increased by 100%. On the other hand, the female-to-female spread of obesity was not significant, with a 38% increased chance. Finally, for friends of the opposite sex, there was even less association between friendship and the spread of obesity.
As we can see, the closeness of friendships may indicate the spread of obesity. Having obese social contacts might change a person's tolerance for being obese or influence their adoption of specific behaviors (e.g., smoking, eating, and exercising). Whereas increasing social distance appeared to decrease the effect of an alter on an ego, increasing geographic distance did not. These results suggest that social distance plays a more substantial role than geographic distance in the spread of behaviors or norms associated with obesity. Whether someone is in another country is less important than how you feel about them.
Social distance is variable, and the type of friendship is important. Between mutual friends, an individual’s risk of obesity increased by 171% if one of the friends became obese. In contrast, there was no statistically meaningful relationship when the friendship was one-sided. Thus, influence in friendship ties appeared to be directional. Christakis’ study suggests that obesity may spread in social networks in a quantifiable and discernable pattern that depends on the nature of social ties. Moreover, social distance appears to be more important than geographic distance within these networks.
So, what can we conclude? Christakis’ study shows that who you hang around with influences your behavior. Dr. Christakis claims, “People are connected, and so their health is connected.” As it affects society, his larger conclusion is the necessity of “approaching obesity not only as a clinical problem but also as a public health problem.” We can conclude that we need to choose our friends carefully because tastes and habits spread contagiously through friendships. It turns out that the ancients were right after all!
Citations:
Christakis, Nicholas A., and James H. Fowler. "The Spread of Obesity in a Large Social
Network over 32 Years." The New England Journal of Medicine, vol. 357, no. 4, 26 July
2007, pp. 370–379. DOI: 10.1056/NEJMsa066082.
Comments