They have found that by bringing people who had similar traits together into a social network, the individuals picked up a new activity that could bring about healthy lifestyle changes.
Researchers at MIT also found that even people who were obese were more likely to pick up the new activity when grouped with other obese people than when grouped with thinner people.
For the study, the researchers worked with 710 participants, most of whom were women, who had enrolled in an online fitness program. They randomly divided the participants into two groups, in one group people were assigned into networks of friends randomly, while in the other, participants were assigned "health buddies" based on similar age, gender and BMI.
Participants were able to see anonymous profiles of their health buddies, as well as certain fitness activities they did, such as the time they spent exercising and whether they were keeping a "diet diary", writing down the foods they ate.
It was this diary the researchers targeted, seeing whether people began keeping one once others in their group did. The researchers found that being in a network matched for common traits made people three times more likely to adopt the new health habit.
According to Ray Browning, a physiologist at Colorado State University, at the simplest level the new research can be about recognizing the influence of peers.
"Too often, individuals think that the blame for their obesity or lack of physical activity rests solely on their shoulders," Browning said.
"This provides evidence that that's not entirely true.
"It may be very influenced by their social network. It's not an out," he added.
While not well-studied, Browning noted that researchers have observed that some people who sustain weight loss for a long period also change who they spend their time with, like a divorce or a move might be involved.
"Some of those individuals completely change their social network, and get out of one and move into another.
"The social network they land in has more of these healthful behaviours," Browning said.
Therefore, changing one's your behaviours may be easier if you bring someone new into your group, such as a personal trainer, who can bring better habits and activities that promote health.
"Take your social network you have and bring in that seed individual," he added.
The study has been published in the journal Science.