People in the study, who were extremely obese (class III obesity) died nearly 14 years early compared to normally weighed participants.Sandra Cohen-Rose and Colin Rose/Flickr

Suffering from extreme obesity can lead to a dramatic reduction in life expectancy, a new study says.

People in the study, who were extremely obese (class III obesity) died nearly 14 years early compared to normally weighed participants.

"While once a relatively uncommon condition, the prevalence of class III, or extreme, obesity is on the rise. In the United States, for example, six percent of adults are now classified as extremely obese, which, for a person of average height, is more than 100 pounds over the recommended range for normal weight," lead author of the study Dr Cari Kitahara, Division of Cancer Epidemiology and Genetics, NCI, said in a news release. "Prior to our study, little had been known about the risk of premature death associated with extreme obesity."

Researchers from the National Cancer Institute (NCI) in the US based their findings on 20 large studies from the US, Sweden and Australia.

The study used body mass index (BMI), the number calculated from a person's weight and height, to measure the participants' body fat. BMI of 19 to 25 is considered to be an ideal weight, while a BMI above 25 and 30 is taken as overweight and obese.

Participants were divided into five different groups according to their BMI, mainly- normal weight (18.5-24.9), overweight (25-29.9), class I obesity (30.0-34.9), class II obesity (35.0-39.9) and class III obesity (40 and above).

Researchers analysed prevalence of early death in more than 9,500 extremely obese people and compared them to 3,04,000 people with normal weight.

Results showed that the risk of early death went up with an increase in BMI. A significant number of people belonging to the class III obesity group died early from deadly diseases, including cancer, diabetes and heart disease. Having a BMI between 40 and 44.9 or between 55 and 59.9 was associated with dying 6.5 and 13.7 years earlier. The extreme obese group had similar or higher risks than cigarette smokers in the normal weight group.

"Given our findings, it appears that class III obesity is increasing and may soon emerge as a major cause of early death in this and other countries worldwide," senior author of the study, Patricia Hartge, said.

The study reported in PLOS Medicine, comes at a time when obesity has become a major health problem across the world. Nearly 30 percent of the total population in the world is obese or overweight. The condition has long been known to increase the risk of many deadly diseases including strokes, diabetes, metabolic syndrome, sleep apnea, infertility, high blood pressure, coronary heart disease, cancer, hearing loss, joint problems in the hips, knees and lower back.