Watching television is the most damaging activity an inactive child can indulge in, a study has warned.
Exploring the health impact of different types of sedentary behaviour, scientists discovered that high levels of TV viewing were associated with an increased risk of heart disease, compared with other pursuits such as computer use.
It is now hoped that the findings will encourage parents to be more aware of the damaging effects certain activities can have.
Researchers at Canada's Queen's University looked at the relationship between the type of activity and health-related outcomes based on 2527 people aged 6-19 from the National Health and Nutrition Examination Surveys (NHANES) 2003 - 2006.
A cardio-metabolic risk score (CRS) calculated on age, waist circumference, blood pressure and cholesterol levels matched against the type of sedentary behaviour revealed watching TV as the most unhealthy pastime.
Children who spent several hours a day staring at a screen, demonstrated a higher waist circumference and cholesterol levels which can trigger a range of disorders including coronary heart disease, stroke, diabetes, and metabolic syndrome.
Lead researcher Valerie Carson said: 'The take home message is that we want children to be more physically active, but then, at the same time, we need to think about what they're doing the rest of the time.
'Our study suggests we should also limit children's television viewing time.'
It was known that physical activity lowers children's risk of developing heart disease in later life, but physical inactivity does not necessarily increase it.
With this in mind, researchers wanted to explore how different types of sedentary behaviour carry a variety of health risks.
Carson added: 'Even if a child is physically active, this activity is really only making up a short period of their whole day, so it's important to look at other aspects of their day to see what's going on.
'Part of that is the kind of sedentary behaviours they engage in.'
Findings, published in the journal BMC Public Health, outlined that TV viewing can be damaging as it involves little energy and can encourage snacking between meals.
The findings support previous studies.
Researchers from University College London revealed earlier this year that watching TV for four hours a day can double the risk of a heart attack among adults and called for recreational guidelines to be issued.