Toddlers’ TV-viewing habits have a direct impact on their fitness and fatness in later childhood, a study has shown.

Further research will help determine whether the amount of TV exposure is linked to any additional child health indicators, as well as cardiovascular health

Each hour per week of television watched by a two-year-old, corresponded to a reduced level of long jump performance by the age of eight to 10, researchers found.

Every extra hour of weekly TV between the ages of two and four also led to almost half a millimetre increase in waist circumference.

For children watching an average 8.82 hours a week, this amounted to a 0.41cm fatter waistline.

Youngsters exposed to more than 18 hours of TV a week – almost 15 per cent of those studied – were almost a centimetre wider around the middle by 10 years of age.

Lead researcher Linda Pagani, from the University of Montreal, said: “The bottom line is that watching too much television – beyond recommended amounts – is not good.

“These findings support clinical suspicions that more screen time in general contributes to the rise in excess weight in our population.”

Physical fitness was measured by means of a standard long jump test, which provides a good indication of overall athletic ability. Sports such as football, skating and basketball all require “explosive leg strength” which can be assessed by long jump performance.

The scientists found that each weekly hour of TV at two years of age was associated with a reduced jump distance of about a third of a centimetre by the fourth grade.

Dr Pagani said: “Watching more television not only displaces other forms of educational and active leisurely pursuits, but also places them at risk of learning inaccurate information about proper eating.”

Further research will help determine whether the amount of TV exposure is linked to any additional child health indicators, as well as cardiovascular health.