People who are 100 pounds or more overweight are the fastest-growing group of overweight people in the United States, researchers reported Monday.
They found the proportion of the severely obese was 50 percent higher in 2005 than it had been in 2000 -- a startling rate of growth.
"The proportion of people at the high end of the weight scale continues to increase at a brisk rate despite increased public attention on the risks of obesity and the increased use of drastic weight loss strategies such as bariatric surgery," said Roland Sturm, an economist at Rand Corporation, a nonprofit research institute.
"The explosion in the use of bariatric (weight-loss) surgery has made no noticeable dent in the trend of morbid obesity," Sturm added in a statement.
The researchers found that based on self-reported height and weight, which tends to underestimate the weight part, 3 percent of Americans are already severely obese -- defined as having a body mass index of 40 or higher.
Body mass index is calculated by dividing weight by the square of a person's height.
The researchers, whose report will be published later this year in the journal Public Health, found that the proportion of Americans with a BMI of 30 or more increased by 24 percent between 2000 and 2005.
The proportion of people with a BMI of 40 or more increased by 50 percent and the proportion of Americans with a BMI of 50 or more increased by 75 percent.
The number of bariatric procedures, which include stomach stapling and stomach bypass surgery, rose to an estimated 200,000 in 2006 from 13,000 in 1998.
More than 30 percent of Americans are overweight, with a BMI between 25 and 29, and an additional 30 percent are obese, with a BMI of 30 or above.