Researchers suggest this is likely to be because people might snack while they watch, or because they are more likely to watch TV after eating their evening meal which might affect their metabolism.
It could, they say, also be a sign of a more unhealthy lifestyle in general.
Dr Pedro Hallal of Brazil’s Federal University of Pelotas looked at the effect of the Olympics on the general public’s activity levels.
He said that, despite a blip around the Games where people temporarily take up a sport, there is no long-term legacy.
“There’s been no health legacy of the Olympics reported ever, but it’s the perfect time to talk about human movement.”
The scientists said governments should ensure their policies encouraged physical activity – citing the example of a bus scheme where stops are placed further apart to encourage walking – and employers should make it easier for staff to be active during their working day – such as flexible lunch breaks and the provision of showering facilities.
Lisa Young, a physical activity specialist at the British Heart Foundation said: “Although we recognise the link between sedentary behaviour and poor health, we do advocate further research in this area to establish categorical statistics in relation to cardiovascular morbidity and mortality.”
Dr Mike Loosemore, from the English Institute of Sport, said: “An hour of brisk walking is hard work this is essentially moderate exercise, I suspect not many people would be able to manage that amount of moderate activity a day.
“So if you change the guidelines then it puts them even further out of reach of the people who would benefit most from increasing their physical activity, which are those that do very little.
“For the vast majority of people while the best way to stay healthy would be to do an hour of moderate activity a day, realistically the best place to start is reducing your sedentary behaviour at work by sitting less and try to increase whatever physical activity you are doing.”