In my previous posting, I reviewed a paper published in the New England Journal of Medicine, which showed that obesity can spread among friends and family just like any infectious disease. But unlike infectious diseases, physical proximity did not count for much: Obesity did not spread among neighbors. It did spread among family members, regardless of geographical location. The strongest influence on the spread of obesity was friendship, in particular, mutual friendship. This was a totally unexpected finding.

The paper had some unavoidable flaws. For instance, in assessing the effect of friendship, the investigators had data on an average of 0.7 “contacts” (or friends) per case. This hardly gives a complete picture of the social network of the average person. So, at this stage, I am skeptical but hope I am wrong. I hope that additional studies will corroborate the basic finding of the relationship between social contacts and disease. Why?


Our current understanding of disease

We have been educated to look for physical explanations to biological/medical phenomena. As physicians, we were taught to look for the “disease genes” ( for instance, Huntington’s disease, sometimes called Guthrie’s disease after the famous folk singer Woodie Guthrie who died of this disease), or the metabolic dysfunction (diabetes type 2), or environmental influences (lead poisoning, pollution-induced respiratory diseases), or a combination of those (cancer as a consequence of genetic predisposition and environmental mutation-causing substances). We viewed with suspicion the ancient art of “alternative medicine”, in my view, justifiably so. When subjected to rigorous scientific examination, most, if not all, of those folk remedies turned out to be just, well, folktales.

But “hard science” Medicine is also wanting, and the example at hand is the spread of obesity. Several genes that predispose to obesity have been identified, but they account for only a minority of cases of the “disease”. What accounts for the rest? We all answer reflexively: lifestyle. But that’s too glib. Why do some people have to fight mightily to avoid obesity, while others barely move off the couch with nary an ounce of weight gain? Again, metabolic differences sometimes exist, but, many times, they are at least not readily apparent.


Enter social networks

The surprising finding that friendships are powerful factors in the spread of obesity, if corroborated, would go a long way toward explaining the puzzle of the “obesity epidemic”. And not only obesity. Many other diseases are now becoming susceptible to this analysis. Why is it that we are having an “autism epidemic”? Why is it that certain school districts have an inordinately higher prevalence of autism? No suspected physical agent, including the much-abused vaccination of children, stood the test of rigorous examination. Increased awareness? Erroneous or loose diagnoses? They don’t account for the rise.

The possibilities are even more amazing. If you examine the genes of obesity and diabetes type 2, you’d find that these two diseases share at least three genes, which raises the possibility that there exist networks of diseases, all interlinked. This may explain, at least in part, why a certain drug given for disease A would affect disease B, or cause side effects unforeseen by our knowledge of the drug’s mechanism. A wonderful example is the drug imatinib (or Gleevec), designed to work specifically on a mutation of the enzyme tyrosine kinase (called Bcr-Abl) that causes CML or Chronic Myelogenous Leukemia. Lo and behold, despite its great specificity, it turned out to inhibit another tyrosine kinase called c-kit, that is responsible for rare a stomach cancer called stromal tumor. What’s the connection? The drug action uncovered an unsuspected close link between the two enzymes; both evolved from a common ancestor gene, and the two cousin proteins resemble each other like twins. But wait, there is more… even more unexpectedly, it was discovered that the drug activates a certain immune cell (IKDC) that is active in killing infectious organisms and tumor cells. The mechanism for that is largely unknown. This is only one example, but it hints at, as yet, undiscovered complex networks of diseases.

Question. All these examples deal with molecular networks, which makes it intuitively easy to visualize interactions between molecules and the effect of these interactions rippling through the networks. But how would something spread through social networks? The answer: Through memes.


Memes, and spread of ideas (and diseases)

What is a meme? The definition I like the best is from the Wikipedia:

meme, (IPA: /mi:m/) as defined within memetic theory, comprises a unit of cultural information, cultural evolution or diffusion that propagates from one mind to another analogously to the way in which a gene propagates from one organism to another as a unit of genetic information and of biological evolution. Multiple memes may propagate as cooperative groups called memeplexes (meme complexes).

Biologist and evolutionary theorist Richard Dawkins coined the term meme in 1976 in his book “The Selfish Gene“. He gave as examples tunes, catch-phrases, beliefs, clothing fashions, ways of making pots, and the technology of building arches.

Amazing; units of cultural evolution spread like genes or viruses, which like genes, are packets of DNA or RNA, and obeying Darwinian laws. No wonder we use such phrases as “an infectious idea” or “the virus of extremism”. Or here is David Brooks of the New York Times on the subject of naming newborns:

“Naming fashion doesn’t just move a little. It swings back and forth. People who haven’t spent a nanosecond thinking about the letter K get swept up in a social contagion and suddenly they’ve got a Keisha and a Kody. They may think they’re making an individual statement, but, in fact, their choices are shaped by the networks around them.”

Well, networks networks everywhere… from the molecular level to the cellular level to whole organisms to social units to nations to the whole human race. I remember reading in the early 70s the essays of Lewis Thomas, “Notes of a Biology Watcher”, published periodically in the New England Journal of Medicine. It was poetry in science, and science in poetry. This is from his introduction to the collection of his essays, “The Lives of a Cell”:

Viewed from the distance of the moon, the astonishing thing about the earth, catching the breath, is that it is alive. And later: It has the organized, self-contained look of a live creature, full of information, marvelously skilled in handling the sun.

In today’s less poetic terminology, we could call this earth-creature “an infinitely interconnected complex of networks”.


The battle of the memes

Memes, like genes, spread among people, only they do it a lot faster. The idea of agriculture, invented in Anatolia (today’s Turkey) about 10,000 years ago, spread all the way to the Iberian Peninsula within 2,000 years. This is lightning speed, considering that a new mutation would need hundreds of thousands of years to establish itself in a given population. Or take the meme of the industrial revolution: Within 100 years, industry spread throughout the “industrial world” of today. Or the computer, or the iPhone, or… what’s the next meme to spread like a virus throughout the world?

But not all memes are created equal. Like genes, they have to be accepted by the individual’s mind, and if need be, demolish competing memes. An example is the idea (or meme) of monotheism, displacing polytheism that had reigned supreme for thousands of years. What was needed for it to triumph was the cultural readiness to be accepted. The early Christians were mocked, tortured, and fed to the lions. But with time, they became tolerated, tacitly accepted, and finally, following an approval from an authority figure (Emperor Constantine, 312 A.D.), the whole Roman Empire converted. Mind you, the people did not have to be coerced—they were ready, the meme of Christianity had already infected them.


What does all that have to do with obesity?

Just like many other memes, the beginning of the obesity meme may have been hard. The sight of an obese person clashed with the body image of most people. An obese woman in shorts? Unheard of! With time, with more and more obese people in shorts and swimsuits, it ceased to be novel; in fact, it became sort of accepted. And the road from acceptance of obesity to the powerful influence of an obese friend on his close friends to become obese is quite short and plausible.

Why doesn’t it work in the other direction, you might ask? Why doesn’t the thin person influence his or her obese friends? I think the answer lies in the biology. Our metabolism is geared toward storage of energy as fat. To go the other way is energetically (in the metabolic sense) and psychologically an uphill battle. So in the battle of the memes, obesity wins because biology is on its side.


Are we doomed to everlasting obesity?

A perfect example of how to win the battle of competing memes is the reversal of the smoking epidemic. Education and peer pressure rendered our mind “unready” to accept smoking despite its addictive properties. Intensive education, coupled with unrelenting peer pressure and regulation can form a countervailing force to resist the path of least resistance offered by the biology.

Will it work? There are encouraging signs. There is a website,, that brings together people who are trying to lose weight, and even more difficult—to maintain it. The whole premise is for the members of this network to publish daily their diet, their elation at success, and the heartbreak of failure. The other members of the network are supportive, encouraging, and when appropriate, dispense some tough love. Judging from the enthusiastic testimonials and almost fanatical belief in the network’s help, it works. Yes, these are still testimonials, but to paraphrase Senator Everett Dirksen, a testimonial here, a testimonial there, and pretty soon you are talking real sample.



So here we are, at the end of our journey through biological networks, linked to social networks, and then completing the circle in the biological network again. I fervently hope that it will turn out to be true. Wouldn’t it be wonderful if the World-Wide Web assumed a new meaning, that of a brand new vision of life on earth? All interconnected, all intimately dependent on all.

Dov Michaeli, MD, PhD
Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.


  1. Microsoft, HP, etc. will see another reason for business becoming softer. It is simply the rise of Apple which is slowly but surely becoming the next giant of tech. I started to predict to friends last year that Apple will become the dominant force in tech within a decade. I have loved Apple products for close to two decades. Now having purchased an iPhone ( I am even more sure that Apple’s growth will be HUGE. The iPhone is not simply a phone but my second mobile computer which makes life much productive, rewarding, and lots of fun.

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