Washington, July 9 (IANS) Adults with extreme obesity have increased risk of dying at a young age from cancer and many other causes, including heart disease, stroke, diabetes, and kidney and liver diseases, says a new research.

People with class III (or extreme) obesity had a dramatic reduction in life expectancy compared with people of normal weight, the findings showed.

"While once a relatively uncommon condition, the prevalence of class III, or extreme, obesity is on the rise," said Cari Kitahara from the National Cancer Institute (NCI), part of the National Institutes of Health in the US.

In the United States, for example, six percent 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, Kitahara explained.

In the study, researchers classified participants according to their body mass index (BMI), which is a measure of total body fat and is calculated by dividing a person's weight in kilograms by their height in metres squared.

BMI classifications (kilogram/metre-squared) for class III obesity is 40 or higher.

The study involved analysis of data pooled from 20 large studies of people from three countries - the US, Sweden and Australia.

"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 from NCI added.

The findings appeared in the journal PLOS Medicine.