Male drivers who are involved in a car crash are more likely to die if they are obese, a US study suggests.
Male drivers with a BMI above 35 were more likely to die, the study found
The Milwaukee team says this may be due to the driver's greater momentum in a crash and because of the effect obesity has on the body's ability to recover.
But the bodies of moderately overweight men appear to cushion the blow, reports the American Journal of Public Health.
The authors said their findings, based on crash data involving 22,000 people, had implications for vehicle design.
The team from the Injury Research Centre of the Medical College of Wisconsin looked at information on 22,000 people from a nationwide crash data collection programme sponsored by the US Department of Transportation.
The fatality rate for motor vehicle crashes was 0.87% for male drivers and 0.43% for women drivers.
The team found that male drivers who had a body mass index that was either higher than 35 or lower than 22 had a "significantly increased risk of death" compared to those with an intermediate body mass index (BMI).
BMI is calculated by dividing your weight in kilograms by the square of your height in metres and is a standard way of assessing whether a person is underweight, overweight or within a healthy weight range.
Lead author Professor Shankuan Zhu said: "The increased risk for death due to motor vehicle crashes associated with a high BMI may be caused by some combination of momentum effects, comorbidities (associated diseases) of obesity, and emergency post-operative treatment problems among the obese.
"Furthermore, obesity imparts anatomical and physiological changes that may either protect or interfere with the body's response to injury."
He said the increased risk for those with a BMI lower than 25 may be because they lack some fat which could provide a cushion effect and absorb some of the energy of the crash.
"It may also be because the reason they are thin is because they have some underlying disease," he added.
But there was no significant link between BMI and women drivers' risk of death, the researchers found.
They suggest the reasons for gender difference in BMI and motor vehicle fatality might be due in part to the different male and female body shapes.
The team argues that its research highlights another major health risk associated with obesity among men and may help the identification of high-risk drivers.
They also argue it could have implications for traffic safety policy and motor vehicle design.
A spokesman for the Royal Society for the Prevention of Accidents said the research was interesting.
"However, it would be a very costly process to have a car modelled on the person's shape to make it as safe as possible - that's really a bespoke car and would take a lot of money and effort to produce," he said.
"It would be preferable to try to stop people having car accidents in the first place."
Dr Colin Waine, chairman of the National Obesity Forum, said the research reiterated the fact that obesity is related to over 40 conditions that affect morbidity, mortality and quality of life.
He added: "People who are obese probably have an adverse risk profile and as such are less able to withstand adverse effects on the body and serious injury."