Every two hours a day spent watching the tube was associated with a 14 percent increase in the risk of diabetes, says a report in the April 9 issue of the Journal of the American Medical Association. And if you're thinking about your looks, that two-hour-a-day stint is associated with a 23 percent increase in obesity, says the report by Dr. Frank B. Hu and colleagues at the Harvard School of Public Health and Brigham and Women's Hospital.
The conclusions come from the 50,000-strong Nurses' Health Study, a long-running project tracking the health of women.
Just sitting around in general is bad for you, public health authorities agree. But motionless TV watching is especially bad because it results in a lower metabolic rate than other sit-down activities, such as sewing, playing board games, driving a car or even just reading, which means putting on more fat that can tip the balance toward diabetes, the report says.
It's not just that being a couch potato in general is bad, the researchers say. The women who spent more time watching TV also had bad eating habits, putting away more the high-calorie, fat-rich foods associated with both heart disease and diabetes, an eating pattern "which is directly related to commercial advertisements and food cues appearing on TV," the study says.
The net result: more than 3,750 women who had a body-mass index under 30, the point at which obesity begins, became obese during the six years of the study, and 1,515 women developed Type 2 diabetes. The link between TV watching and diabetes was clear when the results were adjusted to take into account factors such as smoking, age, exercise levels and diet.
"This is pretty robust data," says Dr. Francine Kaufman, an endocrinologist at Children's Hospital in Los Angeles who is president of the American Diabetes Association. "It confirms the studies in children showing that stopping sedentary behavior has an immense effect on health. We've known this intuitively, and now we have good evidence for it."
The heart people as well as the diabetes people are pushing for a simple remedy to the problem, Kaufman says: Just stand up and walk. The recommendation is for a minimum of a 30-minute brisk walk every day, five days a week.
Kaufman acknowledges that the way our society is built, with families living in suburbs that require a car ride to get anywhere and workers sitting at desks all day, makes it hard for most people to fit a long walk into their everyday activity. She has some suggestions. If you work on a high floor, walk down instead of taking the elevator. When you go for lunch, don't duck into the nearest place, but walk a few blocks.
And Hu, who is associate professor of nutrition and epidemiology at the Harvard School of Public Health, notes in a statement that "even doing chores around the yard and house can help."
The study suggests an even more basic measure. Turning off the TV set and standing or walking around the home for two hours a day reduces the risk of obesity by 9 percent and the risk of diabetes by 12 percent, it found.