OBESE people face a much higher risk of dying in a car crash than people of normal weight, researchers report.
The cause could be that safety in cars is engineered for people of normal weight, not for the obese, they said.
Transport safety scientists Thomas Rice of the University of California at Berkeley and Motao Zhu of the University of West Virginia delved into a US databank on road accidents, the Fatality Analysis Reporting System (FARS).
They dug out data from 1996 to 2008, covering more than 57,000 collisions that involved two cars. This was whittled down to cases in which both parties involved in the collision had been driving vehicles of similar size and types.
The team then compared the risk of fatality against the victim's estimated body mass index (BMI).
The researchers found an increase in risk of 19 per cent for underweight drivers compared with counterparts of normal weight.
For those who were overweight, the increased risk was 21 per cent. The risk increased to 51 per cent for significantly overweight people and to 80 per cent for extremely overweight people.
Obese women were at greater risk than obese men.
The estimates were made after potentially confounding factors -- age and alcohol use, for instance -- were taken into account.
Further work is needed to explain the big differences, but the researchers noted that obese people suffer different injuries from normal-weight individuals in car accidents.
Data from intensive-care units say that obese patients tend to have more chest injuries and fewer head injuries, are likelier to have more complications, require longer hospital stays, and are likelier to die of their injuries.
Another question is whether obese people use their seat belt correctly, rather than leave it unbuckled or partially fastened because it is uncomfortable, and whether safety designs in cars are flawed.
Crash tests, conducted with cadavers, found that in a frontal collision, people of normal weight lurched forward slightly before the seat belt engaged the pelvis bone to prevent further movement, says the study.
But obese cadavers moved substantially forward from the seat, especially in the lower body. This was because abdominal fat acted as a spongy padding, slowing the time it took for the belt to tighten across the lap.
Originally published as Obese have fat chance in a crash