Study Links Social Networks of Family and Friends to Obesity

People wondering about excessive weight gain might look to their relationships with family and friends for one clue, says new research reported in the New England Journal of Medicine.

The study shows that obesity spreads within social networks and that the closer the social connection - even if people live in different households many miles apart - the greater the influence on developing obesity.

The study is the first to provide a detailed picture of the social networks involved in obesity and could prove useful in developing both clinical and public health interventions for obesity.

Nearly one in three American adults, 66 million men and women, are obese, which puts them at risk for a number of serious health problems, including type 2 diabetes, heart disease, and stroke.

"With the sharply rising rates of obesity in this country, we need to learn as much as we can about contributing factors," says National Institute on Aging (NIA)  Director Dr. Richard J. Hodes.

“This study describes social network influences that might be an important part of that equation,” says Dr. Hodes.

Relationships over Decades Studied

A sedentary lifestyle and increased consumption of high-calorie foods are critical factors in the steep rise in the prevalence of obesity, the researchers note.

But they suggest that influence exists among family and friends on developing obesity, in which the attitudes, behaviors, and acceptance of obesity also might play an important role.

To explore whether obesity spreads from person to person within social networks, the research team gleaned weight, height, and other data from the records of 5,124 Framingham Heart Study  participants at up to seven time points between 1971 and 2003.

In addition, they analyzed similar information from the Framingham records of the parents, spouses, siblings, children, and close friends of the key participants.

Together, these individuals formed a large, intertwined social web totaling 12,067 people. The average age of key participants at the inception of the study was 38 years, with a range of 21 to 70 years.

"We were able to reconstruct a large network of individuals who had been repeatedly weighed over time as part of the Framingham Heart Study, and we could see that as one person gained weight, those around him or her gained weight," says Dr. Nicholas Christakis of Harvard Medical School.

"We didn't find that people who were overweight simply flocked together,” he says. “Rather, we found what seemed to be a spread of obesity and that the likelihood of a person becoming obese depended on the nature of the relationship."

Friendship the Strongest Factor

Richard Suzman, Ph.D., of the NIA  says, "The rising rate of obesity threatens to reverse the decline in disability in the older population, with major implications for the health care system."

He notes that this study breaks important new ground in showing how social networks may amplify other factors and help account for the dramatic increase in obesity.

Findings include:

• A key participant's chances of becoming obese increased by 57 percent if he or she had a close friend who became obese.

• In same-sex friendships, a close friend becoming obese increased a key participant's chance of becoming obese by 71 percent. However, no such association was found in opposite-sex friendships.

• The perception of friendship also was an important factor. When two people identified each other as close friends, the key participant's risk of becoming obese increased by 171 percent if his or her friend became obese. In contrast, a key participant was not likely to become obese if someone claimed a close friendship with him or her but the key participant did not report the friendship.

• Among pairs of siblings, one's becoming obese increased the other's chance of becoming obese by 40 percent. This finding was more marked among same-sex siblings than opposite-sex siblings.

• In married couples, one spouse's becoming obese increased the likelihood of the other spouse becoming obese by 37 percent. Husbands and wives appeared to affect each other equally.

• Obesity spread across social ties, despite geographic distance from one person to another.

• Further, social distance - the degree of social separation between two people in the network - appeared to make more of a difference than geographic distance in the spread of behaviors and norms associated with obesity.

• An immediate neighbor's becoming obese did not affect a person's risk of becoming obese.

• Smoking behavior was not associated with the spread of obesity from person to person.

"We identified distinct clusters of obese people within social networks, and the clusters spread about three people deep," says Dr. Christakis.

"People who were only one degree removed from each other socially, such as siblings or close friends, influenced one another twice as much as people who were two degrees removed from each other," explains Dr. Christakis.

Always consult your physician for more information.

Obesity Prevention Tips

Obesity is a chronic disease affecting increasing numbers of children and adolescents as well as adults.

Obesity rates among children in the US have doubled since 1980 and have tripled for adolescents.

More than 15 percent of children aged six to 19 are considered overweight compared to over 60 percent of adults who are considered overweight or obese.

Earlier onset of type 2 diabetes, cardiovascular disease, and obesity-related depression in children and adolescents is being seen by healthcare professionals.

The longer a person is obese, the more significant obesity-related risk factors become.

Given the chronic diseases and conditions associated with obesity and the fact that obesity is difficult to treat, prevention is extremely important.

A primary reason that prevention of obesity is so vital in children is because the likelihood of childhood obesity persisting into adulthood is thought to increase as the child ages.

Many of the strategies that produce successful weight loss and maintenance help prevent obesity. Improving eating habits and increasing physical activity play a vital role in preventing obesity.

Experts provide basic recommendations for adults.

Eat five to nine servings of fruits and vegetables daily. A vegetable serving is one cup of raw vegetables or one-half cup of cooked vegetables or vegetable juice.

A fruit serving is one piece of small to medium fresh fruit, one-half cup of canned or fresh fruit or fruit juice, or one-fourth cup of dried fruit.

Choose whole grain foods such as brown rice and whole wheat bread. Avoid highly processed foods made with refined white sugar, flour, and saturated fat.

Weigh and measure food in order to be able to gain an understanding of portion sizes.

For example, a 3-ounce serving of meat is the size of a deck of cards. Avoid supersized menu items.

Balance the food “checkbook.” Taking in more calories than are expended for energy will result in weight gain. Regularly monitor weight.

Avoid foods that are high in “energy density,” or that have a lot of calories in a small amount of food. For example, a large cheeseburger with a large order of fries may have almost 1,000 calories and 30 or more grams of fat.

By ordering a grilled chicken sandwich or a plain hamburger and a small salad with low-fat dressing, you can avoid hundreds of calories and eliminate much of the fat intake.

For dessert, have fruit or a piece of angel food cake rather than the “death by chocolate” special or three pieces of home-made pie.

Remember that much may be achieved with proper choices in serving sizes.

Accumulate at least 30 minutes or more of moderate-intensity activity on most, or preferably all, days of the week. Examples of moderate intensity exercise are walking a 15-minute mile, or weeding and hoeing a garden.

Look for opportunities during the day to perform even ten or 15 minutes of some type of activity, such as walking around the block or up and down a few flights of stairs.

Always consult your physician for more information.