PROBLEM: There has been a lot of interest lately in ways we can use Internet behavior to monitor public health. Facebook likes seem to be a good tool for this -- researchers have already figured out how to use interests expressed on the site to make strong inferences about users' race, gender, age, political affiliation, and sexual orientation. They can even indicate mortality rates for hospitals.
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METHODOLOGY: Researchers at Harvard Medical School took behavior either positively or negatively linked to obesity -- namely, being active or being sedentary -- and then looked at the proportion of adults who liked related things on Facebook. Relevant pages were broadly categorized underneath "health and fitness" and "outdoor physical activities" for being physically active and "television" for being sedentary. They organized the data by city for all of the U.S. and, in a more focused analysis, by zip code for New York City, and then compared what they found to public data on the prevalence of obesity in those areas.
RESULTS: The greatest interest in physical activity was found in Coeur d'Alene, Idaho, with 25.4 percent of users liking it on Facebook; the least -- 1.3 percent -- was in Kansas City, Missouri. Likes for TV-watching ranged from 50.3 percent in Eugene-Springfield, Oregon to 76 percent in Myrtle Beach, South Carolina. In New York, physical activity was least popular in Southwest Queens (7.6 percent) and most popular in Coney Island (11.2 percent); interest in television was lowest in Greenpoint (64 percent) and highest in Northeast Bronx (70.6 percent).
In any given area, having a greater proportion of people with activity-related Facebook interests, and a smaller proportion who like television, was associated with a lower prevalence of obesity. Obesity and overweight was 12 percent lower in places across the U.S. where the most people were interested in physical activity as compared to where the least people were. In NYC, there was a similar trend, but it wasn't statistically significant. Conversely, TV-watching wasn't significantly associated with obesity for the U.S. sample (although again, the trend suggested a relationship), but in NYC it represented a 27.5 percent increase in obesity between the areas of least and most likes.
IMPLICATIONS: The association between Facebook likes and obesity wasn't perfect, and wasn't always predictive, but it provided strong evidence for there being a relationship between the lifestyle habits people endorse online and their real-world health. That relationship, write the authors, "could be harnessed for intelligently targeted health interventions, such as through online and mobile messaging." There's no way of knowing how may people will lie about their interests to avoid getting spam that implores them to go jogging, but it could be worth a shot.
"Assessing the Online Social Environment for Surveillance of Obesity Prevalence" is published in PLoS ONE.