The average person in the UK spends over 2,5 hours watching TV every day – that’s more time than on their social life, hobbies, playing sport and reading put together, according to the Office of National Statistics.

Even more astounding, children aged 11 to 15 now spend a massive 53 hours a week - seven and a half hours a day – watching TV and playing on their computers, an increase of 40 per cent in just a decade.

Couch Potato

Research has found time and again that the more TV you watch, the fatter you’ll be. In fact, scientists say TV is largely to blame for the fact that childhood obesity has literally doubled in the last generation.

It makes sense: the more TV you watch, the less active you will be. So while it’s recommended that you take around 10 000 steps a day doing your everyday activities (and fit, active people generally make the grade), watching TV cuts down on your total by an average of 520 fewer steps.

"Clearly the more time a person spends watching television the less time they have to be physically active," concludes Harvard Medical School researcher Dr Gary Bennett.

And replacing TV with exercise for as little as 15 minutes a day could make a difference. (Read more: Childhood Obesity 'Solved by Moderate Exercise').

Sugar High

"The problem stems from the fact that watching television is a sedentary activity but it's much more than that," adds scientist Dr Ross E. Andersen. "Children are watching TV, many times eating high calorie and fat snack foods, and watching commercials for fast food, all of which encourage more eating."

Not only will you be less active, but the more TV you watch, the more calories, fatty foods and fizzy drinks you are likely to consume, and the less healthy nutritious foods you’ll eat. One study, for example, found that girls who watched five or more hours of TV a day consumed 175 more calories daily than girls who watched one hour or less.

Research has also shown that the barrage of information about food that TV presents confuses people, especially kids, about healthy eating – and the more television they watch, the more confused they are about which foods will help them grow up strong and healthy. Children who watch a lot of TV also believe that “diet” or “fat free” means “nutritious,” probably because TV advertising intentionally blurs the lines between the two.

Diabetes Risk

Eating fast food and watching TV add up to a high risk for obesity and diabetes. People who watch TV are less active – a major diabetes risk – and are twice as likely to eat regular high-fat fast food meals, missing out on healthy fruits, veggies and whole grains. Those who watch TV for more than three hours a week and eat fast food more than twice a week are three times more likely to have abnormal glucose metabolism.

Obesity and abnormal glucose control are both strong risk factors for heart disease, strokes and Type 2 diabetes.

There’s also a direct link between the inactive lifestyles of heavy TV viewers and high blood pressure – even in young teenagers, and regardless of being overweight or not. High blood pressure is a massive risk factor for strokes, heart disease and diabetes.(Read more: Living with High Blood Pressure).

Psychological Trauma

And as if that’s not scary enough, consider this: TV has also been linked to psychological issues like aggression and depression. Believe it or not, several studies have found that long hours of passive TV viewing (usually for around six hours a day) causes significantly elevated levels of psychological trauma. In one study, about a third of children who were heavy TV viewers scored in the clinical range for one or more symptoms of psychological trauma.

"These children are at high risk for having a serious problem and should be assessed by a mental health professional," warns social work professor Mark I. Singer. He said that negative effects included anxiety, depression, anger, posttraumatic stress and dissociation.

And even though it’s an unfashionable theory, children who watch a lot of violent TV really are more angry and aggressive, research has shown repeatedly.

These emotions in turn negatively affect physical health, causing your body wear and tear. (Read more: Mindset Matters).

Too much TV also negatively affects work and school life, hindering your ability to concentrate and perform. School children who watch the most TV are at the top of the scale for attention deficit disorder, restlessness, confusion and poor quality homework.

Convinced? Then take part in TV Turn-Off week, 23rd – 29th April. For details, Click Here.

Get fit as a family with an action-packed holiday (Read more: Active Ways To Beat Child Obesity).