Extreme obesity may shorten life expectancy up to 14 years, according to a recent study the Los Angeles Times reported.

Researchers from the National Cancer Institute (NCI), part of the National Institutes of Health, found that people with class III, or extreme, obesity had a dramatic reduction in life expectancy compared with people of normal weight. They have increased risks of dying at a young age from cancer and many other causes including heart disease, stroke, diabetes, and kidney and liver diseases.

"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," Cari Kitahara, lead author of the study, said in a statement. "Prior to our study, little had been known about the risk of premature death associated with extreme obesity."

For the study, the research team analyzed data pooled from 20 large studies of people from the United States, Sweden and Australia.

After excluding individuals who had ever smoked or had a history of certain diseases, the researchers evaluated the risk of premature death overall and the risk of premature death from specific causes in more than 9,500 individuals who were class III obese and 304,000 others who were classified as normal weight.

Based on their findings, the risk of dying overall and from most major health causes rose continuously with increasing body mass index within the class III obesity group.

Researchers said the accuracy of the study findings is limited by the use of mostly self-reported height and weight measurements and by the use of BMI as the sole measure of obesity. However, they said the results highlight the need to develop more effective interventions to combat the growing public health problem of extreme obesity.

"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," Patricia Hartge, senior author of the study, added.

The findings were recently published in PLOS Medicine.