People who spend a lot of time watching TV are more likely to die prematurely or get cancer or heart disease, according to research.
A study says those who sit in front of a television or computer screen instead of being active are more likely to become ill or die because of their lifestyle.
Researchers at Glasgow University say the impact of being a couch potato is nearly twice as bad for people who do not exercise.
Although more hours spent in front of a screen increases the risk of early death or disease for everyone, it is less serious for people who are otherwise fit and strong.
Scientists say the findings could help improve health advice to target people with sedentary lifestyles.
If people watch a lot of television or spend a lot of time on their computer instead of exercising, they are more likely to become ill than those who exercise as well
The research compared the lifestyles of more than 390,000 people and found people who spend the most time in front of a screen are more likely to be obese and have linked conditions such as diabetes or high blood pressure.
They are also more likely to be a smoker, have high cholesterol, eat more processed meat and fewer fruits and vegetables, and to do less exercise.
These people are more likely to develop cancer or heart disease or die because of their sedentary lifestyles.
If people who have the same amount of screen time are fit, however, they are less likely to be affected by the same illnesses.
Increasing strength and fitness may avoid bad effects of screen time
Increasing strength and fitness may offset the unhealthy effects of spending a lot of leisure time sitting down and watching a screen, according to the authors.
Dr Carlos Celis, author of the study said: ‘Our study shows that the risks associated with sedentary behaviour are not the same for everyone.
‘Individuals with low physical activity experience the greatest adverse effects.
‘This has potential implications for public health guidance as it suggests that specifically targeting people with low fitness and strength for interventions to reduce the time they spend sitting down may be an effective approach.’
How the research was carried out
The researchers used detailed information about 390,089 people to do the study – including their gender, weight, hours spent in front of a screen, time spent exercising, their education and income, and details of their diet and health.
They found that people who spent more hours in front of a screen had a higher risk of premature death, or developing cancer of heart disease.
However, if people with a lot of screen time were fit and strong their risk was lower than sedentary people in the same category.
Scientists measured people’s fitness by their grip strength – which they suggest could be an easy way for authorities to target those who are most at risk.
People with a weaker grip are more likely to be sedentary and at risk of an early death, whereas a stronger grip indicates better overall fitness and a lower risk.
Dr Celis added: ‘While fitness testing can be difficult in healthcare and community settings, grip strength is a quick, simple and cheap measure.
‘Therefore it would be easy to implement as a screening tool.’
The study is published in the journal BMC Medicine today.
Binge-watching could cause blood clots
A recent analysis suggested binge-watching your television shows almost doubles the chance of fatal blood clots.
People who say they ‘very often’ sit down in front of the TV screen face a 1.7 times higher risk of venous thromboembolism (VTE).
This is the umbrella term for deep vein thrombosis, a clot in the legs, and pulmonary embolism, when the clot travels to the lungs.
Prolonged sitting can in some cases lead to blood clots because normal circulation of blood through the legs and feet is impaired.
However, researchers discovered exercising may not even counter the damaging effects of sitting down for such long periods of time.
They found the risk of VTE remained high even when weight and exercise levels were taken into account.
The conclusion adds to the growing array of evidence highlighting the dangers of watching TV, the most common sedentary behaviour around the world.