The level of obesity in Australia has more than doubled in the last two decades because of the rise in more sedentary lifestyles, according to a recent medical survey.

The nationwide study of 11,247 people over the age of 25 found 39% to be overweight and 20.8% obese, reported BBC News Online. The levels were 2.5 times higher than the levels found in a similar study in 1980.

“This urgently demands action on many levels to prevent further rises in the prevalence of diseases such as type two diabetes,” the researchers who carried out the study said in their report published in the Medical Journal of Australia.

The researchers found that obesity was slightly more common in women, with 22.2% of women obese compared to 19.3% of men. However, the percentage of people who were classed as overweight was higher among men – 48.2%, compared with 29.9% of women.

“Lower educational status, higher television viewing time and lower physical activity time were each strongly associated with obesity, with television viewing time showing a stronger relationship than physical activity time,” the survey said, as quoted by BBC News Online.

“Strong positive associations between obesity and each of television viewing time and lower physical activity time confirm the influence of sedentary lifestyles.”