Research paper
Christakis NA, Fowler JH. The spread of obesity in a large social network over 32 years. N Engl J Med. 2007 Jul 26;357(4):370-9. doi:10.1056/NEJMsa066082
Why we cite it
Landmark study analyzing 12,067 people in the Framingham Heart Study over 32 years (1971-2003) to quantify the spread of obesity through social networks. Found that a person’s chance of becoming obese increased 57% if a friend became obese, 40% for siblings, and 37% for spouses. Effects were strongest among same-sex relationships and extended to three degrees of separation. Geographic distance did not matter — social distance was the relevant factor. Despite subsequent methodological critiques (econometric reanalyses found effects reduced when addressing homophily and shared-environment confounds), the paper fundamentally reframed the public health conversation by highlighting social network effects on weight outcomes.
About the author
Nicholas A. Christakis — BS (Yale, 1984). MD (Harvard Medical School, 1989). MPH (Harvard School of Public Health, 1989). PhD Sociology (University of Pennsylvania, 1995). At time of paper: Professor of Sociology and Medicine, Harvard University. Currently: Sterling Professor of Social and Natural Science, Yale University (2018-present) — Sterling is Yale’s highest faculty honor. Director, Human Nature Lab. Co-director, Yale Institute for Network Science. Elected to National Academy of Medicine (2006), AAAS Fellow (2010), American Academy of Arts and Sciences Fellow (2017), National Academy of Sciences (2024). Co-author of Connected (2009, with Fowler; 20 language translations).
James H. Fowler — Born 1970. PhD Government (Harvard University, 2003). Professor of Political Science and Medicine, UC San Diego. Research: social networks, behavioral economics, evolutionary game theory, genopolitics. Guggenheim Fellow. Named to Foreign Policy’s Top 100 Global Thinkers. 40+ publications in Nature, Science, PNAS, NEJM, BMJ.