Time to put down the remote? TV time is linked with obesity, diabetes and other health problems in adults.(Photo: Getty Images/iStockphoto)

It's late September, time for many adults to settle in for a new season of prime-time drama, comedy, sports, reality competition and the occasional three-hour political debate.

But as you get comfy on your sofa, you might want to consider this: Your TV habit might be killing you. A growing body of evidence links not just sitting in general but TV viewing in particular with all sorts of health problems. Those include obesity, Type 2 diabetes, heart disease and, yes, premature death.

Too much TV "is a really serious health hazard," says Frank Hu, a professor of nutrition and epidemiology at Harvard University. For example:

• In a review of eight studies by Hu and colleagues, each two-hour increase in daily TV viewing was associated with a 20% increased risk of Type 2 diabetes, a 13% increased risk of cardiovascular disease and a 13% increased risk of death from any cause – translating to 104 extra deaths each year for every 100,000 people.

• An Australian study that included only physically active adults – those getting at least 150 minutes a week of moderate to vigorous exercise – found that increases in TV time were linked with increases in waist size, blood pressure and blood glucose in both men and women and increases in harmful blood fats in women.

• Overweight U.S. adults followed for an average of three years in a diabetes prevention trial were 3.4% more likely to develop diabetes for each daily hour they spent watching TV.

Of course, we've been hearing for years that all the hours we spend sitting – including at work, while commuting or even while virtuously reading a book – are linked with health problems. That's why treadmill desks were invented.

But outside of work, and in retirement, we still do lots of sitting, and "TV is a huge part of people's leisure sitting," says Bonny Rockette-Wagner, a University of Pittsburgh researcher who worked on the diabetes prevention study.

How much? Even with the growth of smartphones, tablets, online video and other alternative distractions, . adults on average spend more than five hours a day watching live or time-shifted TV, according to Nielsen, the TV ratings company. The U.S. Department of Labor and other researchers, relying on different survey methods, put the total at a lower two to three hours a day. Nielson and other sources agree that adults over 50 watch far more than younger adults.

The sheer time spent sitting to watch TV can explain a lot of its effect, Rockette-Wagner says. But there may be something, or some things, especially bad about TV sitting, Hu says.

"There is some evidence that the resting metabolic rate is actually lower when you watch TV, compared to some other sedentary behaviors like reading or driving," he says.

Translation: You might burn fewer calories draped on the sofa watching TV than you do turning pages or working the gas pedal. "You have more than 100 channels on a remote control, you are just sitting there and you don't need to move your feet at all," Hu says.

TV watchers, unlike readers, also "get bombarded with junk-food commercials and commercials for soft drinks," Hu says. And sure enough, he says, "people who watch a lot of TV eat more junk food, drink more soda and consume more calories."

Prolonged sitting plus mindless eating can be a "double whammy," says psychologist Delia West, a professor in the department of exercise science at the University of South Carolina.

So, is it time for TV time limits akin to the two hours a day now recommended for children? Hu says that's "reasonable."

But others say there's not yet enough evidence to support any specific limit on TV time or, for that matter, overall sitting time. "We can say that the more you limit extended periods of sitting, the better," says Peter Katzmarzyk, an obesity and diabetes researcher at Louisiana State University. And, no matter how much time you spend sitting, it's still important to aim for 150 minutes a week or more of moderate to vigorous activity, such as brisk walking or running – guidelines that are backed by strong science, he says.

"We can say we need to reduce the amount of time we spend watching TV and being sedentary," West says. Some of her tips for doing that:

• Track how much time you spend sitting and watching TV. Just knowing your number might motivate you to lower it.

• Try a week without TV (there's an official Screen-Free Week in May aimed especially at families with children). See how it affects the way you feel and what you do with your time.

• If a week seems impossible, start by lowering your TV time by half an hour a day.

• Stand up, run in place or wander around the house during commercials.

• Ban eating in front of the TV. You may be less likely to eat mindlessly if you do it elsewhere.

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