Overweight and obese men are three times more likely than women to die early, the authors of an international study have found.
An analysis of 3.9 million healthy non-smokers, published in the The Lancet journal on Thursday, found that the excess risk of premature death (dying before the age 70) increases by more than 10 per cent in moderately obese men.
The study was done by the Global BMI Mortality Collaboration, led by Britain's Cambridge University, and looked at more than 200 studies of people aged 20 to 90 years old from 32 countries, including Australia.
Researchers used the World Health Organisation's body mass index scale for weight, excluded anyone with chronic health conditions, and only used cohorts which had been followed up at least five years later.
They found that on average, overweight people lose one year of life expectancy while moderately obese people lose about three years.
If Australia's overweight and obese population were within the normal weight range, about one in six premature deaths could potentially be avoided, according to the authors.
Some experts have warned the results may be skewed by the broad ages of those studied - men generally having a shorter life expectancy than women - and limitations in methodology, including limiting the study to BMI only.
The data showed that men and women with a normal BMI (in the range 18.5 – 25) have a 19 per cent and 11 per cent chance respectively of dying early. But for those with a BMI of 30 to 35, that increases to 29.5 per cent for men and 14.6 per cent for women.
"We also found that men who were obese were at much higher risk of premature death than obese women," lead investigator Dr Emanuele Di Angelantonio said.
"This is consistent with previous observations that obese men have greater insulin resistance, liver fat levels and diabetes risk than women."
Academics from the National Cancer Institute, National Institutes of Health, Bethesda wrote in response to the research that there were methodological limitations of global studies measuring BMI and mortality.
"To date, few sufficiently sized randomised trials have been done to address whether weight-loss interventions reduce mortality or morbidity," they wrote.
Professor John Dixon, head of Melbourne's Baker IDI's obesity laboratory, said the age at which a person became overweight was an important factor in premature death risk.
"If you're obese when you're young, you're likely to have many more years lost than if you're obese when you're old," he said, adding that people over 65 years could be overweight and have "no risk at all of premature death".
"In fact they've got some advantage," he said.
"The message really should be if you're young, if you're under the age of 65 and you're obese, you should be doing something about it," Professor Dixon said.
Epidemiologist Anna Peeters, head of Obesity and Population Health at Deakin University, said the loss of three years was a better outcome for obese men than seen in older studies.
"That's decreased over time because we treat things like diabetes and heart disease so much better," she said.
