Generous portions of TV make women fat:

No one in her right mind would associate a lot of TV watching with a healthy lifestyle. Now a new study of more than 50,000 women over a period of six years backs common sense with scientific support.

The first study to compare the effects of inactivity on obesity and diabetes concludes that being a couch potato significantly raises the risk of both diseases.

“Our data provide strong evidence that sedentary behaviors, especially prolonged TV watching, are directly related to the risk of obesity and type 2 diabetes,” reports Frank Hu, leader of a team from the Harvard School of Public Health and the Harvard Medical School that did the research. “In contrast, even light to moderate activity, such as walking and housework, substantially lowers the risk.”

Previous studies have shown that children who watch too much TV gain too much weight. A different Harvard investigation, called the Health Professionals Follow-up Study, found a positive link between heavy TV viewing and type 2 diabetes.

In the latest effort, part of the Nurses Health Study, researchers followed 50,277 women from 1992 to 1998. In 1992, these women boasted body mass indexes (BMI) of less than 30. A score of 30 ranks a person as obese – a woman 5 feet tall with a BMI of 30 would weigh 155 pounds or more; a 5-foot-6-inch woman would weigh 180 pounds or more; and a 5-foot-9-inch female would weigh 200 pounds or more. The women also had no diagnosed diabetes, heart disease, or cancer.

By 1998, 3,757 of the nurses reached or topped the obesity level and 1,515 developed type 2 diabetes. With age, smoking, exercise activity, and diet factored out, each two hours per day of TV watching was statistically associated with a 23 percent jump in obesity and a 14 percent rise in diabetes.

In contrast, each one hour a day of brisk walking (4 mph or faster) reduced obesity 24 percent and diabetes 34 percent. Even standing or walking around at home 2 hours a day reduced obesity 9 percent and diabetes 12 percent.

Hu and his colleagues estimate that a whopping 1,127 new cases of obesity and 651 new cases of diabetes could have been prevented by “a relatively active lifestyle.” Specifically, they cite less than 10 hours per week of TV watching and at least 30 minutes a day of brisk walking.

Obesity epidemic

The Harvard scientists speculate that “increasing sedentary behaviors, especially TV watching, may have contributed to the present obesity epidemic in the United States.”

Rates of both obesity and diabetes are accelerating in the United States and in many other nations. Obesity in this country has nearly doubled to 21 percent or more than one out of every five adults, according to the federal Centers for Disease Control and Prevention. More than 14 million people have type 2 diabetes, though only about half of them know it. More than 625,000 cases will be diagnosed this year.

In parallel with this, a 1997 survey concluded that adult women spend approximately 34 hours a week in front of a TV screen. Men watch 29 hours of TV a week. There’s been a steady increase in the number of homes with multiple TVs, video recorders and players, and the ubiquitous remotes.

“Compared with other sedentary activities such as sewing, playing board games, reading, writing, and driving a car, TV watching results in lower energy expenditure,” Hu and his colleagues point out. “Constant exposure to food advertising leads to increased food and calorie intake and unhealthy eating patterns.” On top of that, women who watch a lot of TV are more likely to smoke and drink alcohol and less likely to exercise.

To Hu and his colleagues, the simple act of sitting around less can go a long way toward reducing sickness and early death. Obesity and diabetes are prime risk factors for heart disease, the leading killer of people in developed countries. In their report, published in the April 9 issue of the Journal of the American Medical Association, the researchers recommend that “public health campaigns to reduce obesity and diabetes risk should not only promote increasing exercise levels, but also decreasing sedentary behavior, especially prolonged TV watching.” Substantial health benefits can be gained by substituting “even light to moderate activity such as doing household chores and walking.”