Childhood obesity rates are leveling off in America, but a new sub-category within the clinical definition of obesity is growing. Called "severely obese," it affects an estimated 4 million American kids and teens--about 5 percent of children. More from NBC News:
That means nearly 4 million U.S. youth fall into a new category of obesity risk, one that carries dangers of serious disease and early death, even beyond expected harms, according to a scientific statement published Monday by the American Heart Association.
"It appears that severe obesity is the fastest-growing subcategory of obesity in youth," write the authors in the report published in the journal Circulation.
Worse, when children get that big, it's difficult to help them lose weight with traditional tools of diet and exercise, or even with drugs and surgery.
"Once this problem gets so severe, there's no turning back, or there's no turning back easily," said Dr. Thomas Inge, a co-author of the paper and director of the Center for Bariatric Research and Innovation at Cincinnati Children's Hospital Medical Center. "People don't like to hear that and they don't like to know that."
Severely obese kids have higher rates of weight-related disease, including type 2 diabetes and cardiovascular disease, with complications such as high blood pressure and hardening of the arteries. Previous research has shown that obese kids as young as age 10 can have the arteries of middle-aged adults.
The new class encompasses kids ages 2 to 19 who have a body-mass index, or BMI, that's 20 percent higher than the 95th percentile for their gender and age, or a BMI score of 35 or higher. A child or teen in the 95th percentile weighs more than 95 percent of others his or her age.
Image: Overweight pre-teen with salad, via Shutterstock