People who want to reduce their risk of developing a chronic disease should cut the number of hours they spend in front of the TV, the World Cancer Research Fund (WCRF) has said.

According to the fund, it is already well established that leading a sedentary lifestyle can lead to obesity, which increases the risk of a number of diseases, including type 2 diabetes, heart disease and some types of cancer.

However, it emphasised that sedentary behaviour, such as sitting or lying down, does not just refer to a lack of physical activity. In fact, a person can exercise every day and still lead a sedentary lifestyle.

"People often assume that sedentary behaviour is the same as physical inactivity. But someone can do the recommended amount of daily physical activity but still be sedentary, for example, by spending an hour at the gym, then sitting at their desk all day and on the sofa in the evening," explained the WCRF's head of health information, Kate Mendoza.

She noted that research by the Broadcasters' Audience Research Board in the UK found that the average adult watches over 28 hours of television per week. That means that if a person lives to the age of 80, they will have spent over 13 years watching television.

Meanwhile other research suggests that people in developed countries spend over 15 hours a day engaged in sedentary behaviour.

"With a labour-saving device for most tasks, a large proportion of the population spends a significant part of the day sitting down. If people were to reduce prolonged periods of sedentary behaviour, they would reduce their risk of serious diseases, including cancer," Ms Mendoza insisted.

The WCRF said that while research in this field is relatively new, the key appears to be interrupting prolonged periods of sedentary behaviour.

"At work, regular breaks such as getting up to speak to a colleague or making a drink will reduce sitting time, while at home, setting quotas for watching television or using a computer can also help," it suggested.