Health Spectator

Could your ever-expanding waistline be more a reflection of the friends you keep than of a personal lack of restraint? Or could whatever maladaptive eating and exercise habits you’ve acquired be a reflection of social acclimation rather than merely foibles you’ve fomented on your own?

Questions such as these arise as one reads through a recent article published in The New England Journal of Medicine by Nicholas A. Christakis and James H. Fowler. What we find most troubling about the findings presented by these researchers is their plausibility.

No reasonable theory we have previously heard regarding obesity has, to our recollection, treated it as a social disease. (Excuse our re-casting the term, but we believe it is even more applicable here than in its normal usage.) We have always been attracted to the view that obesity is simply a perversion of the natural tendency to gain weight in preparation for winter, when food in nature is scarce. In our modern world—in which winter tends to be more an annoyance than a period of near-starvation for most of us—this fattening process never stops. When winter never arrives and we never starve, some of us just grow fatter indefinitely.

One interesting theory to explain this weight gain run amok holds that after considering our modern diet, which in no way resembles the food available to our ancestors when our genetic structure was being determined, the modern conveniences of lighting, heating, air conditioning and protective shelter cause most of us to become desynchronized from the natural circadian rhythms that orchestrate our daily hormone cycles and influence many bodily functions, including metabolism. This desynchronization interferes as well with natural sleep, the daily period during which the immune system works overtime while the body repairs itself. In nature, as the periods of darkness wax and wane with the seasons, so too do our bodies (and their sleep cycles) change in a natural rhythm. From this point of view, obesity is just one symptom of a modern, alienated physical state: dis-ease. Depending on the individual, this disease might manifest as schizophrenia, diabetes, cancer… or obesity.

We find it interesting to contemplate that this particular theory does not in any way contradict the notion of obesity as a disease that can spread through social networks much as might, say, venereal diseases, though both the nature of the diseases themselves and the type and degree of contact are quite different. Indeed, one of the most intriguing notions in Christakis and Fowler’s findings is that geographic proximity is not even a factor in the spread of obesity; rather, the relationship between individuals—of which the most influential is strong mutual friendship—becomes the predominant factor.

Thus, social proximity substitutes for physical proximity, and with that substitution, the venereal analogy holds.

Still, our initial reaction upon seeing the title of the paper—The Spread of Obesity in a Large Social Network over 32 years—was somewhere between aghast and scandalized. The whole notion of obesity as a disease that spread from individual to individual—especially outside the genetically linked family structure—seemed preposterous. The authors note that obesity in a valued friend may cause one to become accepting of the condition, thus becoming more susceptible to it oneself or to accepting behaviors that cause it.

Aside from that, nothing in this paper really attempts to explain obesity: rather, it describes a topology by which the condition appears to spread. Nothing here hints at physical mechanisms or causes; we merely see relationships among those affected. An unfortunate implication one might draw from the authors’ analysis is that the obese exercise some unconscious control over their condition. We think this is an all-too-common medical prejudice that so far remains unproven.

Yet, if instead of the notion of accepting obesity one substitutes, say, infection—that is, a non-voluntary mechanism for the spread of obesity in which the infectious agent might be a complex of practices that the individual does not consciously associate with their consequences, rather than an external pathogen—the potential usefulness of the study’s findings falls back into place without unwarranted etiological assumptions.

Not only is it interesting that mutual friendships show the highest correlation among obese individuals, but those friendships between members of the same sex show the highest correlation of all. Not even marriage or sibling relationships correlate individuals as highly for obesity.

Not only do Christakis and Fowler provide thought-provoking insights into obesity, they build on previous work by Christakis and others emphasizing the undeniable importance of social networks in our overall approach to disease, particularly from the public health perspective. Whether this particular work points to a whole new dimension in the study of obesity or proves a tantalizing but inevitable dead end remains to be seen.

One wonders: how would the results of the study have differed had it mapped the spread of television or cell phones instead of obesity?