When it comes to health, Australians are fat, unhappy and leading the world in self-deception.

The latest global survey by medical insurer BUPA has found half the Australians who are overweight do not realise it, and men are more likely to be in denial about their weight.

The findings are part of an international study of 13,000 people from 12 countries.

Melbourne GP Dr Bert Boffa heads BUPA's medical services and says the survey findings are important.

"Sixty per cent of Australians are overweight or obese but only about 30 per cent realise they are, so half of the Australians who are overweight don't realise they are," he said.

Dr Boffa says there is also some significant gender gaps that emerge from the study, with men being less likely to visit a doctor or admit to being overweight.

"They're significantly more self-deceiving, in other words of those men who are overweight and inactive they're more likely to not be aware of that than women who are overweight and inactive," he said.

He also says older Australians are most likely to be unaware they are overweight.

Dr Boffa believes people are not concerned about their weight because of the increasing life expectancy in Australia.

He says Australians are suffering more chronic and disabling health problems rather than the fatal health problems generally associated with obesity, leading to a false sense of security.

Sorry, this audio has expired Global survey finds Australian a fat and sad nation in denial ( Bronwyn Herbert )

"We're one of the most long-lived nations on the planet," he said.

"The rate of heart attack is going down, the rate of stroke is going down, yet we've never been fatter.

"But the reality is that the fact that we're fatter means we are getting more diabetes, more heart disease - although of a more disabling nature rather than having the big heart attacks that we used to get - so in other words, more chronic disease. We're living longer but we risk becoming more disabled."

'Tyranny of normality'

Dr Boffa blames the overall trends in poor health on what he calls the "tyranny of normality".

He says people are fooled into thinking the things they see are normal when that may not be the case, listing increasing obesity rates as an example.

"What's normal today was not normal 50 years ago and people are sort of fooled by what's normal," he said.

"And I think that's what's leading to the complacency."

The other notable finding of the survey is that depression is increasingly prevalent in Australia, with one fifth of respondents saying they had it.

"We have high levels of depression and anxiety, in fact that is obvious to most practising GPs - I've noticed that as well in my own practice - and it seems to be at a younger age as well," Dr Boffa said.

China, New Zealand and Saudi Arabia had the next highest levels of depression, while Thailand had the lowest rate at just 7 per cent.