A new study in the American College of Sports Medicine journal gives evidence that sedentary time, involving prolonged sitting and absence of whole-body movement, is an independent risk factor for several health outcomes.
The study included 2,033 women and 2,031 men, all who reported being physically active at least 2.5 hours a week (30 minutes, 5 days per week). They were also all free of diabetes and heart disease. Researchers then looked at the total number of hours daily spent watching television and compared TV time to the prevalence of metabolic risk factors.
In men they found that as the hours of daily TV viewing increased, so did their:
>Waist circumference (indicating increased abdominal fat)
>Systolic blood pressure
>Blood glucose levels
All increases showed a dose-response relationship (the more TV they watched, the higher their risks). All three of these risks are primary risks for metabolic syndrome, diabetes, and heart disease. These findings were adjusted not only for physical activity but also age, education, smoking, income level, alcohol intake, diet quality, and family history of heart disease or diabetes.
In women they also found a dose response relationship between hours of TV viewing and:
>Waist circumference
>Systolic blood pressure
>Blood glucose levels
>Blood triglyceride levels
>Blood HDL levels
Detrimental health changes were observed in women who watched more than an hour of TV daily, and in men who watched 2 hours or more of TV daily. The highest risks were linked to women watching 2 hours or more of TV daily and men watching 3 or more hours daily.
It appears that, even though all of these people met minimal guidelines for physical activity, long periods of inactivity, such as watching TV, should be considered a unique modifiable behavior, an independent risk factor for metabolic diseases. It seems the body was designed for activity and long periods of inactivity can result in poorer health and increased risk for serious health problems.
Just as there are national guidelines for physical activity, the authors of this study suggest that there also needs to be similar guidelines for inactivity. They suggest no more than 2 hours of leisure-time screen time per day may be a practical starting point. Children are recommended to spend no more than an hour a day of screen time. Persons engaging in more time than this are significantly increasing their risk for obesity, high blood pressure, metabolic syndrome, diabetes, and coronary heart disease.
Excessive TV viewing can now be considered a new risk factor putting people at increased risk for some of our nation's most serious health problems. Excess TV viewing can replace time normally spent in moderate activities such as household chores, gardening, playing with the kids, and other light-intensity activities that contribute to better health in addition to a regular exercise program.
If you just have to watch a favorite, lengthy movie or football game, here is a way to beat the system: Bring your stationary bicycle to the TV, or a treadmill, and put in some active miles while watching. The goal is to avoid long periods of sitting, which is a health hazard.
Reference:
Healy GN, et al. Television time and continuous metabolic risk in physically active adults. Medicine and Science in Sports and Exercise. 2008;40(4):639-645.