OBESE and overweight Australians over the age of 45 are using one in six hospital beds and costing the health sector an extra $4 billion a year.

That was the finding of a joint study by the University of Western Sydney, University of Sydney and the Sax Institute.

The researchers looked at 200,000 hospital records of people aged 45-79 to show just what impact obesity had on hospital costs.

Heavy Cost: the weighty toll of our obesity epidemic

People in the extremely obese weight range had more than double the rate of admissions and days in hospital compared with those of a normal weight.

Even the gear required to cater for overweight patients takes a heavy toll.

Equipment such as hoists, shower chairs and lifters are usually three to four times more expensive than regular equipment.

In 2011-12 there were more than 56,000 public hospital beds in Australia.

One estimate from the Sax Institute put the cost of obesity on hospitals at $4 billion a year, with one in every six dollars spent on hospitalisation going towards the extra cost of catering for the overweight.