Parts Nine and Ten5 min read
Resources and the Research Behind This Module
Talks, books, and every study cited, in plain language so you can check the work.
Everything cited in this module, in plain language, so you can go and check the work yourself. That includes the studies that disagree with the headline in Part One.
Watch and listen
On social networks and health influence
On relationships and long-term health
On sabotage and negative support
On the microbiome finding
Reading
- Christakis, N. A., & Fowler, J. H. (2009). Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives. Little, Brown.
- Christakis, N. A. (2019). Blueprint: The Evolutionary Origins of a Good Society. Little, Brown Spark.
- Waldinger, R., & Schulz, M. (2023). The Good Life: Lessons from the World's Longest Scientific Study of Happiness.
- Background on Nicholas Christakis (opens in a new tab)
- The three degrees of influence rule (opens in a new tab)
- The helper therapy principle (opens in a new tab)
References
Social network influence, original observational work
- Christakis, N. A., & Fowler, J. H. (2007). The spread of obesity in a large social network over 32 years. New England Journal of Medicine, 357(4), 370-379.
- Christakis, N. A., & Fowler, J. H. (2008). The collective dynamics of smoking in a large social network. NEJM, 358(21), 2249-2258.
- Fowler, J. H., & Christakis, N. A. (2008). Dynamic spread of happiness in a large social network. BMJ, 337, a2338.
The critiques (included in the interest of honesty)
- Cohen-Cole, E., & Fletcher, J. M. (2008). Detecting implausible social network effects in acne, height, and headaches.
- Lyons, R. (2011). The spread of evidence-poor medicine via flawed social-network analysis.
- Shalizi, C. R., & Thomas, A. C. (2011). Homophily and contagion are generically confounded in observational social network studies. Sociological Methods & Research.
The experimental evidence that followed
- Kim, D. A., et al. (2015). Social network targeting to maximise population behaviour change: a cluster randomised controlled trial. The Lancet, 386(9989), 145-153.
- Alexander, M., Forastiere, L., Gupta, S., & Christakis, N. A. (2022). Algorithms for seeding social networks can enhance the adoption of a public health intervention in urban India. PNAS, 119(30).
- Airoldi, E. M., & Christakis, N. A. (2024). Induction of social contagion for diverse outcomes in structured experiments in isolated villages. Science, 384(6695).
- Beghini, F., et al. (2024). Gut microbiome strain-sharing within isolated village social networks. Nature, 637, 167-175.
Social support, undermining, and weight outcomes
- Leahey, T. M., et al. (2015). Influence of family, friend and coworker social support and social undermining on weight gain prevention among adults. Obesity.
- Karfopoulou, E., Anastasiou, C. A., Avgeraki, E., Kosmidis, M. H., & Yannakoulia, M. (2016). The role of social support in weight loss maintenance: results from the MedWeight study. Journal of Behavioral Medicine, 39, 511-518.
- Ogden, J., & Quirke-McFarlane, S. (2023). Sabotage, collusion, and being a feeder: towards a new model of negative social support and its impact on weight management. Current Obesity Reports, 12(2), 183-190.
- Chabria, R. S., et al. (2025). Romantic partner undermining in a behavioral weight loss intervention. Journal of Behavioral Medicine.
- Dailey, R. M., et al. (2023). Romantic partner undermining of weight loss. Journal of Health Psychology.
- Powers, T. A., Koestner, R., Denes, A., Cornelius, T., & Gorin, A. A. (2022). Autonomy support in a couples weight loss trial.
- Wing, R. R., & Jeffery, R. W. (1999). Benefits of recruiting participants with friends and increasing social support for weight loss and maintenance. Journal of Consulting and Clinical Psychology.
Interventions and meta-analyses
- Rao, W. W., et al. (2024). The effectiveness of social-support-based weight-loss interventions: a systematic review and meta-analysis. International Journal of Obesity.
- Social media-based interventions for adults with obesity and overweight: a meta-analysis and meta-regression (2023). International Journal of Obesity.
- Nunns, M., et al. (2025). Evaluation of the aspects of digital interventions that successfully support weight loss: systematic review with component network meta-analysis. Journal of Medical Internet Research, 27, e65443.
- Betz, et al. (2026). Identifying social media-based interactions that help adults adhere to weight loss goals: a systematic review. Obesity Reviews.
- Chen, Y., et al. (2021). The effect of peer support on individuals with overweight and obesity: a meta-analysis. Iranian Journal of Public Health, 50(12).
- Gray, C. M., et al. Football Fans in Training (FFIT) program evaluations.
Helper therapy and the benefits of helping
- Riessman, F. (1965). The "helper" therapy principle. Social Work, 10(2), 27-32.
- Pagano, M. E., et al. (2004). Helping other alcoholics in Alcoholics Anonymous and drinking outcomes: findings from Project MATCH. Journal of Studies on Alcohol.
- Zemore, S. E., Kaskutas, L. A., & Ammon, L. N. (2004). In 12-step groups, helping helps the helper. Addiction.
- Luks, A. (1988). Helper's high: volunteering makes people feel good, physically and emotionally.
- Systematic reviews of volunteering and health outcomes in older adults (2023).
Maintenance and the loss/maintenance distinction
- National Weight Control Registry (Wing, R. R., & Hill, J. O.). Ongoing since 1994.
- Harvard Study of Adult Development (Waldinger, R., director). Ongoing since 1938.
- Holt-Lunstad, J., et al. Meta-analytic work on social relationships and mortality risk.