People who are obese are significantly more likely to die in a car crash than their thinner counterparts because they are often propelled further forward in a collision, scientists have claimed. Experts want passenger vehicles redesigned for those who are overweight.

Researchers at the University of California analysed data from the US Fatality Analysis Reporting System between 1996 and 2008. This data showed all records of fatalities from traffic collisions.

During this period, there were 57,591 collisions. The researchers looked at 3,403 pairs of drivers where there was information on weight, age, seatbelt use and airbag deployment.

Half of the drivers were of normal weight, a third were overweight and a fifth were obese.

Two thirds of the sample were male and one in three were aged between 16 and 24. Another third were not wearing a seatbelt properly, and in half of the crashes an airbag was not deployed.

Researchers analysed weight according to World Health Organisation guidelines and split obesity into three categories: Level I for people with a body mass index (BMI) of 30-34.9, and Level II 35-39.9.

Those on Level III have a BMI of 40 or over - morbidly obese.

Underlying health problems

Drivers at Level I were 21 percent more likely to die in a car crash than people of normal weight, and those at Level II were 51 percent more likely. Morbidly obese people were 80 percent more likely to be killed, the scientists found.

A third of adults in the US are obese and the UK is reaching similar levels quickly. It has been predicted that by 2050, 60 percent of men and 50 percent of women will be obese in the UK.

Researchers found that obese women were at greater risk than men. They pointed to other research that suggests obese people's bodies are propelled further forward on impact before the seatbelt engages the pelvis, as the additional fat prevents the belt from fitting properly.

They also suggested obese people are more likely to have underlying health problems that could contribute to the increased risk, but noted that improved car design would help reduce fatalities.

"The ability of passenger vehicles to protect overweight or obese occupants may have increasingly important public health implications, given the continuing obesity epidemic in the US," they said.

"It may be the case that passenger vehicles are well designed to protect normal-weight occupants but are deficient in protecting overweight or obese occupants."