Now our fat friends have something new to worry about.
According to researchers who studied a group of over 12,000 people for more than 32 years, one of the most significant determining factors of obesity is one’s close friends.
The study shows that the influence of a mutual friendship can create an environment in which the friends mirror each other’s behavior and lifestyle—even if they don’t live near each other.
And while the authors do not claim that an actual virus causes obesity, they do emphasize the social "contagion" factor. James Fowler, a political science professor at the University of California, San Diego and co-author of the NEJM study, told reporters, "This is the first [study] to show how obesity spreads through the social network from person to person to person."
"It has become very popular to speak of the obesity epidemic. We began to wonder if it is truly an epidemic," said Dr. Nicholas Christakis, who co-authored the study with Fowler. Dr. Christakis is a medical sociology professor at Harvard Medical School.
The report documented that if a person became obese, his or her friends had a 57 percent higher chance of becoming obese also. If the friendship was a close one and considered mutual by both parties, that risk jumped to 171 percent.
This is a higher risk than that from living with an obese spouse or sibling, leading the researchers to conclude that close relationships were more important in determining weight than genetics (as with a sibling) or in sharing daily lifestyle habits (as with a spouse). When a spouse gained weight, the other spouse had a 37 percent increased risk of becoming overweight. If a man got fat, his brother was 40 percent more likely to do so too.
Fowler and Christakis used the data from over 12,000 people involved in the Framingham health study. The Framingham health study is a long-term analysis of the health habits of people living in Framingham, Massachusetts, which began in 1948. This study used records dating between 1971 and 2003.
What surprised the authors was the fact that close friends continued to be a strong influence even if they did not live near each other. "We were stunned to find that people who were hundreds of miles away had just as much impact on a person’s weight as friends who are next door. This is not due to people eating or exercising together," said Fowler to reporters.
By using such a long-term study, they were able to rule out the idea that overweight people simply chose other friends who were obese—the study tracked friendships from as far back as childhood, where the friends began at different weights.
The conclusion echoes other findings that have attached a contagion-like aspect to certain eating disorders such as anorexia or bulimia.
"What spreads is an idea. As people around you gain weight, your attitudes about what constitutes an acceptable body size changes, and you might follow suit and emulate that body size," said Christakis to reporters. "It may cross some kind of threshold, and you can see an epidemic take off. Once it starts, it’s hard to stop it. It can spread like wildfire."
Indeed, the study showed that the "contagion" could spread from one friendship to another. If a person became overweight as a result of the close friendship, their other friends were also at increased risk of getting fat.
Experts weighing in were optimistic about finding a "cure" for the epidemic. "If close social environments can promote a disease, they can also promote solutions to the disease," William H. Dietz of the Centers for Disease Control and Prevention said to the press. "These same social networks might be used to turn a disease like obesity around."
So if you blame your friend for making you fat, don’t ditch her just yet. The two of you could just as easily influence each other to healthier habits.
According to researchers who studied a group of over 12,000 people for more than 32 years, one of the most significant determining factors of obesity is one’s close friends.
The study shows that the influence of a mutual friendship can create an environment in which the friends mirror each other’s behavior and lifestyle—even if they don’t live near each other.
And while the authors do not claim that an actual virus causes obesity, they do emphasize the social "contagion" factor. James Fowler, a political science professor at the University of California, San Diego and co-author of the NEJM study, told reporters, "This is the first [study] to show how obesity spreads through the social network from person to person to person."
"It has become very popular to speak of the obesity epidemic. We began to wonder if it is truly an epidemic," said Dr. Nicholas Christakis, who co-authored the study with Fowler. Dr. Christakis is a medical sociology professor at Harvard Medical School.
The report documented that if a person became obese, his or her friends had a 57 percent higher chance of becoming obese also. If the friendship was a close one and considered mutual by both parties, that risk jumped to 171 percent.
This is a higher risk than that from living with an obese spouse or sibling, leading the researchers to conclude that close relationships were more important in determining weight than genetics (as with a sibling) or in sharing daily lifestyle habits (as with a spouse). When a spouse gained weight, the other spouse had a 37 percent increased risk of becoming overweight. If a man got fat, his brother was 40 percent more likely to do so too.
Fowler and Christakis used the data from over 12,000 people involved in the Framingham health study. The Framingham health study is a long-term analysis of the health habits of people living in Framingham, Massachusetts, which began in 1948. This study used records dating between 1971 and 2003.
What surprised the authors was the fact that close friends continued to be a strong influence even if they did not live near each other. "We were stunned to find that people who were hundreds of miles away had just as much impact on a person’s weight as friends who are next door. This is not due to people eating or exercising together," said Fowler to reporters.
By using such a long-term study, they were able to rule out the idea that overweight people simply chose other friends who were obese—the study tracked friendships from as far back as childhood, where the friends began at different weights.
The conclusion echoes other findings that have attached a contagion-like aspect to certain eating disorders such as anorexia or bulimia.
"What spreads is an idea. As people around you gain weight, your attitudes about what constitutes an acceptable body size changes, and you might follow suit and emulate that body size," said Christakis to reporters. "It may cross some kind of threshold, and you can see an epidemic take off. Once it starts, it’s hard to stop it. It can spread like wildfire."
Indeed, the study showed that the "contagion" could spread from one friendship to another. If a person became overweight as a result of the close friendship, their other friends were also at increased risk of getting fat.
Experts weighing in were optimistic about finding a "cure" for the epidemic. "If close social environments can promote a disease, they can also promote solutions to the disease," William H. Dietz of the Centers for Disease Control and Prevention said to the press. "These same social networks might be used to turn a disease like obesity around."
So if you blame your friend for making you fat, don’t ditch her just yet. The two of you could just as easily influence each other to healthier habits.
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