April 8, 2003 (New York) -- Couch potatoes, beware! TV watching is strongly linked to weight gain -- and even light activity can go a long way to preventing the obesity and diabetes that commonly follows.
For the first time, new research provides proof of what many have suspected for years -- couch potatoes and weight gain go hand in hand. But the health risks don't just end there. The study also shows that too much TV watching dramatically raises the risk of developing type 2 diabetes.
In addition, the health risks associated with television watching were significantly greater than those associated with other sedentary activities, such as sewing, reading, or driving a car. Researchers say TV watching seems to be particularly effective at promoting weight gain because it not only reduces physical activity, but it also encourages people to eat more and eat unhealthy foods due to advertising and other food cues on TV.
"Couch potatoes don't move and eat more," says researcher Frank Hu, MD, PhD, of the Harvard School of Public Health. "This is the first scientific study to prove this relationship."
Hu presented the results of his study, which appears in April 9 issue of The Journal of the American Medical Association, today at a media briefing on obesity in New York City.
More weight-loss news from a special obesity issue of The Journal of the American Medical Association.
The study compared television viewing habits of more than 50,000 women who participated in the Nurses' Health Study from 1992 to 1998. During the six years of follow-up, 7.5% of the women became obese and 1,515 women developed type 2 diabetes.
Obesity is generally defined as having a body mass index (BMI, a measurement of weight in relationship to height) of 30 or more, or weighing 20% or more than the recommended weight.
Researchers found that as TV watching increased, weight gain also increased -- leading to more obesity and diabetes. For each two-hour increase in television watching per day, there was a 23% rise in obesity and 14% increase in the risk of diabetes.
Although other sedentary activities also increased the risk of weight gain and diabetes, their impact was much smaller than the women's television viewing habits. For example, each additional two hours of sitting at work or driving a car was associated with a 5% increase in obesity and 7% increase in diabetes.
But the researchers found that even light activity can fight weight gain. The study showed that for each hour of brisk walking per day the women did, there was a 24% reduction in the risk of obesity and a 34% drop in diabetes risk.
Hu says those findings suggest that public health campaigns should not only promote increasing physical activity but they should also recommend a decrease in sedentary activities, like television watching.
"TV watching is the most prevalent and pervasive sedentary behavior in the U.S.," says Hu. "It's second only to the time we spend in bed."
Studies show the average American male spends an average of 29 hours per week watching television and the average American woman spends 34 hours per week watching television.
"There should be an upper limit for television watching. No more than 10 hours of TV watching per week, in addition to at least 30 minutes of walking per day," says Hu.
Researchers estimate that 30% of new obesity cases and 43% of new diabetes cases could be prevented by adopting that kind of relatively active lifestyle that limits television watching to less than 10 hours per week and incorporates moderate exercise, such as 30 minutes of brisk walking per day.
"We're not talking about running marathons, but just taking a walk around the park near your house can go a long way in reducing the risk of obesity and type 2 diabetes," says Hu.