DSC5104 - Assignment 2
Obesity & Social Networks
Notes:
1. Try to answer the questions as precisely as possible. You should take no more than 2 pages (i.e. 1 sheet of
paper) for this assignment.
2. Please upload the assignment document in PDF and mention your name and ID inside the document.
4. Submit on or before Mar 27th (Fri) 11.59pm.

Problem context:
Certain research studies have claimed that obesity can spread through social networks, much like how viruses
spread. The authors of the study emphasize that if a person becomes obese, friends of the person are also likely
to get obese in due time. For instance, in a popular study published by the New England Journal of Medicine,
the authors presented a detailed analysis of a large social network of 12,067 people to show that when a person
got obese, it increased the chances of the persons’ friends becoming obese by more than 50%. For more details
on the study and related press coverage please refer to the links below.
Interestingly, the effect of the contagion was not limited to friends alone. The study also found that among adult
siblings, if one of the siblings became obese, it increased the chances of obesity of the other by 40%. Similarly, if
a spouse became obese, it increased the chances of the other spouse becoming obese by more than 30%. No
such effect, however, was observed for neighbors.

Reference Links:
https://www.nytimes.com/2007/07/25/health/25cnd-fat.html
Study: https://www.nejm.org/doi/full/10.1056/NEJMsa066082

Questions:
1. Do you believe the key findings of this study? More specifically, which finding(s) from the study do you
think is more likely/less likely to be true for a general population? (2 marks)
2. What are 2-3 limitations of the given study? You can include any limitations related to the formulation
of the research questions, study design, quality of data, analysis of results, and interpretation of
findings. (3 marks)
3. What are some general methodological challenges (not limited to the ones specific to this study)
associated with assessing peer influence in networks? (2 marks)
4. If you had to answer the same question raised in the study (i.e. does obesity spread through a social
network?), how would you design a study to answer this question (e.g. conduct a randomized lab/field
experiment, analyze a specific type of historical dataset etc.)? (3 marks)