A study by the University of Queensland found that Australians over 60-years watched on average four hours of television a day, about an hour longer than younger adults.
Researchers found that, for each hour a person spends watching TV, their risk of developing metabolic syndrome increases.
The study, led by Dr Paul Gardiner from UQ's School of Population Health, was one of the first to examine the effects of sedentary behaviour and TV watching on older men and women.
"Up until now, most research about sitting and watching TV has been focused on children, while older adults have potentially the most to gain from changing their behaviour," Gardiner said.
Gardiner said even light activity, such as folding washing while watching TV, can reduce the risk of developing metabolic syndrome.
"Reducing sedentary behaviour may be a feasible and practical way for older adults to improve their health and may be particularly important for those whose health or physical functioning limits their participation in moderate-intensity physical activity," he said.
Previous studies had shown that sedentary behaviour has a unique physiological effect on the body and that this was different from the effect of lack of exercise.