There’s a potential added benefit to eating with a colleague at lunch versus dining alone: if they choose a healthy option, you may be more inclined to do the same.
But there’s a downside too: if they pick an unhealthy option, you may be more likely to choose that too.
Researchers from Massachusetts General Hospital’s Mongan Institute Health Policy Research Center discovered this after a study of around 6,000 MGH employees. The results were published Thursday in the peer-reviewed journal Nature Human Behaviour.
“We found that individuals tend to mirror the food choices of others in their social circles, which may explain one way obesity spreads through social networks,” lead author Douglas Levy, Ph.D., an investigator at the Mongan Institute Health Policy Research Center, said in a press release.
For two years, the study followed the eating habits of a diverse employee group as they dined at the hospital system’s seven cafeterias. Using the cafeteria’s traffic light system, researchers determined the healthfulness of the employee’s meals. Healthy food and drinks are green, less healthy purchases are yellow and unhealthy ones are red.
Researchers could gather information on individual food purchases from employees’ ID cards, which can be used to buy meals. Using the time between people’s food purchases, researchers inferred participants’ social networks. They also evaluated how many minutes apart two people made food purchases, the frequency that people ate at the same time over several weeks and if two people visited a different cafeteria simultaneously.
“Two people who make purchases within two minutes of each other, for example, are more likely to know each other than those who make purchases 30 minutes apart,” Levy said.
Over 1,000 participants were asked to confirm the names of the people researchers identified as their eating partners, too. Doing this validated the social network model.
“A novel aspect of our study was to combine complementary types of data and to borrow tools from social network analysis to examine how the eating behaviors of a large group of employees were socially connected over a long period of time,” said coauthor Mark Pachucki, Ph.D., associate professor of Sociology at the University of Massachusetts, Amherst.
Assessments of three million instances of two employees led researchers to determine the pairs’ food purchases were more likely the same than different.
“The effect size was a bit stronger for healthy foods than for unhealthy foods,” Levy said.
As for why people usually choose the same foods when eating together, the reason could be peer pressure.
“People may change their behavior to cement the relationship with someone in their social circle,” Levy said.
Further, the researcher wrote in Behavioural & Social Sciences about the public health implications of this study’s results.
“Indeed, additional work is needed to test whether and how social influence may be harnessed to improve healthy eating,” Levy wrote. “Social influence may also play an important role in public health through a network multiplier or peer effect — interventions targeting a narrowly defined group may nevertheless have broader impact as the affected individuals influence those around them”
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