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Kids' Rates of Severe Obesity Are Troubling, Researchers Say

The obesity rate in children hasn't declined in recent years, and severe obesity may even be on the rise, a new study has found. The findings follow a recent report showing a decline in obesity in young children.

In the new study, which included data from about 27,000 children ages 2 to 19 in all parts of the Unites States, researchers examined changes in the rate of different classes of obesity, including severe obesity, between 1999 and 2012.

They found an upward trend in all rates of obesity in U.S. children over the study period, including the rate of severe obesity, in which children either have a body mass index (BMI) greater than 35, or they weigh at least 20 percent greater than that of children already considered to be obese. [10 Ways to Promote Kids' Healthy Eating Habits]

"An increase in more severe forms of obesity in children is particularly troubling," said study researcher Asheley Cockrell Skinner, an assistant professor of pediatrics at the University of North Carolina School of Medicine. "Extreme obesity is more clearly associated with heart disease and diabetes risk in children and adolescents, and is more difficult to treat."

However, the results didn't show a significant change — neither a decline nor an increase — in overall rates of obesity in the most recent years of the study, between 2009 and 2012, suggesting that the trend of rising obesity may now be stabilizing.

In 2011 to 2012, more than 32 percent of children ages 2 to 19 were overweight, 17 percent were obese and about 8 percent were severely obese, according to the study, published today (April 7) in the journal JAMA Pediatrics.

The findings appear to contradict the results of a recent study that found a decline in obesity among low-income preschoolers. That study used the same data set as the current study, but it looked at a shorter time period.

"Both our study and the prior one used the National Health and Nutrition Examination Survey. However, the earlier study examined only the last decade, while we make use of all available years — from 1999 to 2012," Skinner said. "In 2003, there was an unusual uptick in obesity among young children, which led to the appearance of a significant decline. However, when we look at the bigger picture, that change is not there."

Moreover, examining only the overall rates of obesity would mask upward trends of the less common but more dangerous form of severe obesity over time, the researchers said.

In the study, children who had a BMI greater than 85 percent of their peers' were considered overweight, and children who had a BMI greater than 95 percent of children of their same age and gender were considered obese.

Severe forms of obesity are called class 2 and class 3 obesity, and are defined as having a BMI greater than 35 or 40, respectively.

For example, a 10-year-old boy of average height for his age (4 feet 6 inches) would be considered obese if he weighed 95 pounds. He would be considered Class 2 obese if he weighed 115 pounds and class 3 obese if he weighed 130 pounds.

In 2012, 5 to 6 percent of children were class 2 obese, and about 2 percent were class 3 obese, the researchers estimated.

Email Bahar Gholipour. Follow us @LiveScience, Facebook & Google+. Original article on Live Science.