Rates of childhood overweight and obesity have not decreased in the U.S. in recent years, and severe obesity is on the rise, especially for minority children, according to a new study.

Ten percent of teens now have severe obesity, lead researcher Asheley Skinner of the Duke Clinical Research Institute told Reuters Health by phone.

The public health campaigns and White House initiatives targeting childhood obesity in recent years have stressed staying active and making healthy food choices. That advice may be more effective for kids who are not yet overweight or obese than for those who are already obese, Skinner said.

"We don't know what this trend would look like without those initiatives but we're certainly not seeing a reversal," she said.

Kids with severe obesity often "need more intensive interventions, beginning with the healthcare system, with pediatricians or family providers," Skinner said.

The researchers used National Health and Nutrition Examination Survey data from 1999 through 2014 for children ages two to 19. During that time, all classes of obesity continued to increase, in particular severe obesity for children and teens, which usually means being at least 100 pounds overweight.

In 2013 and 2014, 33 percent of children were overweight and 17 percent were obese, Skinner and colleagues reported in Obesity.

Obesity increased over time for teens of both sexes, and was consistently more common for black and Hispanic children than for white children.

"The data suggest that over six million children and adolescents have severe obesity," Dr. William Dietz of George Washington University wrote in a commentary published with the study report.

Another analysis which also used NHANES data but started in the 2003 cycle instead of the 1999 cycle concluded that obesity among kids and teens did not change over time, and obesity among two- to five-year-olds fell over time from 14 to 8 percent, Dietz wrote. Neither conclusion is necessarily wrong, but relying on NHANES data alone doesn't provide conclusive information on the obesity epidemic, he wrote.

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There is evidence, however, that people have started to consume less sugary drinks, fast food and pizza over the last decade, Dietz wrote.

Obesity is increasing in a similar way in other countries, Skinner said.

Kids with severe obesity need 20 or 30 hours of interaction with a care provider, which is more than a general practitioner can provide, she said.

"Oftentimes an insurance company will reimburse for a primary care visit but not a YMCA membership, and there can be other structural barriers like time and school," Skinner said.

"There's no one thing we have to do, if we're going to reverse this we're going to have to do a lot of things," she said.