It's been a decade since the U.S. surgeon general declared that childhood obesity has become an epidemic.

That clarion call triggered a wave of private and public programs designed to get kids to swap video games and greasy burgers for workouts and plates of vegetables and fruit.

Graphic: Childhood obesity

The results haven't been encouraging.

The proportion of obese U.S. children ages 2 to 19 rose from 13.9 percent in 1999 to 16.3 percent in 2006, the most recent year for statistics from the federal Centers for Disease Control and Prevention. The 2006 figure climbs to 32 percent when overweight children are added to the mix.

California's trend has been equally gloomy. Between 2003 and 2005, the prevalence of obese adolescents ages 12 to 17 rose from 13.9 percent to 19.8 percent, according to a newly released study by researchers at the University of California Los Angeles.

Health officials use gender, age and body mass to calculate whether a child is overweight or obese. For example, a 10-year-old boy with a body mass index of 23 is considered obese. A 12-year-old boy with the same BMI is overweight. A 15-year-old boy with the same BMI is considered healthy.

As more children put on excess pounds, obesity-related health problems – many that could affect these children for the rest of their lives – continue to mount.

Pediatricians increasingly are treating young patients with hypertension, sleep apnea, diabetes and orthopedic issues traditionally not seen until adulthood.

The medical complications, along with social ostracism, diminish the quality of life for obese children, according to a study published in 2003 by researchers from the University of California San Diego, Rady Children's Hospital in Kearny Mesa and Texas A&M University.

Science is helping doctors better understand why many youngsters and adults can't seem to shed pounds through diet and exercise once they've packed on an excessive amount of weight.

“It turns out that once you're about 100 pounds over your ideal body weight, your body has reset its thermostat,” said Dr. Sunil Bhoyrul, a bariatric surgeon in San Diego.

The process works this way: Overeating produces an oversupply of insulin, which causes the body to use more of its energy to store fat. That tricks the body into thinking it's being starved when it isn't. The body responds by lowering physical activity, increasing hunger pangs and converting even more energy into fat.

“This is not about a habit that has gone bad. This is about a physiological illness,” Bhoyrul said.

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