How bad is watching TV for your health?

Each hour spent watching TV daily increases the chance of developing diabetes by 3.4pc in high-risk individuals, research has suggested.

A study carried out in the United States looked at data from more than 3,000 overweight adults participating in a Diabetes Prevention Programme (DPP) who were given either a placebo, metformin drug (used for diabetes) or took part in a lifestyle intervention scheme.

Researchers looked at whether, as well as increasing activity levels, the lifestyle intervention also made those taking part spend less time sitting.

Prior to the trial all three groups had reported spending an average of around two hours and 20 minutes a day watching TV.

But the team found that while the placebo and metformin groups spent an average of just nine and six minutes less in front of the TV respectively, those taking part in the lifestyle scheme sat and watched it for 37 minutes less per day on average.

The authors then investigated the impact of sedentary behaviour over time on diabetes incidence and found for all participants, the risk of developing diabetes increased approximately 3.4% for each hour spent watching TV after adjustment for age, sex, intervention and time-dependent leisure physical activity.

''Future lifestyle intervention programmes should emphasise reducing television watching and other sedentary behaviours in addition to increasing physical activity,'' the study said.

The health case against TV

• It can increase the risk of diabetes
• It can be damaging for children's mental health
• It can increase children's blood pressure
• Experts say it is as dangerous as smoking or being overweight

The TV case for TV

• The Wire
• Game of Thrones
• Line of Duty
• The Fall

^{Game of Thrones: Among the best TV ever made?}

Researchers also found that subsequent changes in body weight may account for some of the relationship between sitting behaviour changes and diabetes development.

Senior author Dr Andrea Kriska, of the University of Pittsburgh, Pennsylvania, said: ''These findings are particularly noteworthy because a decrease in sitting occurred, despite the absence of programme goals aimed at reducing sitting.

''It is likely that a lifestyle intervention programme that incorporates a specific goal of decreasing sitting time would result in greater changes in sitting and likely more health improvements than are demonstrated here.

''Finally, these results should inform future intervention efforts that already focus on goals of increasing activity and reducing weight to also consider emphasising sitting less.''

The study is published in Diabetologia (the journal of the European Association for the Study of Diabetes).

Previously Joy Whitby, the award-winning producer of many of Britain’s most beloved children’s programmes, called for under-5s to be banned from watching TV.

Saying there had been a total loss of any “sense of occasion” as a result of so much television, she added she would not allow a child under five to watch programmes alone.

Whitby, who is still making television shows at the age of 82, said: “If I had a child under 5 at home again, I wouldn’t want to leave him in front of the television set unsupervised if I could possibly help it.

It has also been claimed that watching TV for more than two hours a day increases the risk of raised blood pressure in children.

Children aged two to 10 who spent this much time in front of a TV or computer screen were 30 per cent more likely to have high blood pressure than those who did not.

Lack of physical activity increased the risk even more, by 50%, scientists found.

Researchers have also claimed that watching too much TV is as dangerous as smoking or being overweight, and that the “ubiquitous sedentary behaviour” should be seen as a “public health problem”.

Experts from the University of Queensland, Australia, write: “TV viewing time may have adverse health consequences that rival those of lack of physical activity, obesity and smoking; every single hour of TV viewed may shorten life by as much as 22 minutes.”

Referring to Australian and American guidelines that suggest children should spend no more than two hours a day in front of a screen, the academics conclude: “With further corroborative evidence, a public health case could be made that adults also need to limit the time spent watching TV.”