April 9, 2003

Doctors have studied the television habits of thousands of women and found a strong relationship between how much television they watched over six years and their risk of becoming obese and developing diabetes.

"It's alarming," said Dr. Frank Hu, a scientist at the Harvard School of Public Health and lead author of the study that appears in today's Journal of the American Medical Association. "A couch potato has a significantly elevated risk for obesity and diabetes."

In 1992, the researchers began to gauge how many hours 70,000 women enrolled in the Nurses Health Study spent watching TV. Among the women, 3,700 new cases of obesity and 1,500 new cases of type 2 diabetes were logged at the end of six years. Obesity is a major risk factor for diabetes.

Researchers found that three hours of television viewing a day led to a twofold increase in obesity and 50 percent increase in diabetes.

Each two-hour-per-day increment of TV was associated with a 23 percent increase in obesity and a 14 percent increase in the risk for type 2 diabetes.

Women who reported one hour of television a week had an average body mass index (BMI) of 25; women with 40 hours a week television time had an average BMI of 28. (BMI is a person's weight in kilograms divided by height in meters squared. A number over 25 is considered overweight; over 30 is obese.) Hu found that those who spent more time watching TV ate more red meat, snacks, refined carbohydrates and sweets and were less likely to eat fruits and vegetables.

Hu said brisk walking for an hour a day was associated with a 24 percent reduction in obesity and a 34 percent lowering of diabetes. Working around the house or standing for two hours a day reduced the risk of obesity by 9 percent and diabetes by 12 percent. He calculated that reducing TV viewing to less than 10 hours a week, and adding a 30-minute brisk walk to the day, could have prevented 30 percent of the new obesity cases and 43 percent of the type 2 diabetes cases.

In other findings, Columbia University's Stanley Heshka of the New York Obesity Research Center at St. Luke's/Roosevelt Hospital carried out a two-year study comparing a popular diet program, Weight Watchers, to a self-help program. More than 420 obese men and women were assigned to either program; of the 310 who completed the study, those on Weight Watchers were more successful in losing weight and keeping it off: 11 pounds at six months and 6.5 pounds after two years. Those in the self-help program lost about 4 pounds at six months and had returned to their pre-diet weight two years later.

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