Running is 15-year-old Maddi Holder's passion. She's on varsity cross-county and junior varsity soccer teams.
But six years ago: "I couldn't do those things and I was incapable of keeping up with my friends, running or jumping around on the playground," said Maddi.
She was in the 90th percentile in weight and couldn't run without getting winded. Even worse, Maddi was on track for a possible diagnosis of fatty liver disease.
"In children with fatty liver disease, their liver fills up with fat and starts to become yellowish," said Columbia University's Dr. Joel E. Lavine. "By the time symptoms ever do present it's oftentimes too late to do much about what's already happened to their liver."
A new report in the Journal of the American Medical Association finds exercise and weight loss are the only ways to reverse it. Researchers tested whether vitamin E and a diabetes drug could treat the liver injury, but scientists found little change.
To make a change for Maddi, her mom enrolled her in the Completely Active Training Zone (CATZ) program for kids.
"In the beginning I definitely didn't want to do anything, and I was really upset and I was scared and I had no confidence at all," said Maddi.
"The number one reason why kids don't want to be active is the fear of failure," said Jim Liston, creator of the CATZ Kids Fitness program.
Liston says kids need a place where they won't get teased, where they can build confidence.
"We need kids to be skilled movers. They need to be able to kick and throw and run and hop and skip and climb trees, and experiment with a number of activities," said Liston.
But experts say getting a child out there to enjoy playing is more than just learning how to run fast. Maddi says the change for her was more than just physical -- it was emotional.
"Once you start and once you come to a place to CATZ and you start building your confidence, then there's no stopping you once you get that far because then you just feel better about yourself, you're more confident, you're happier with your life," said Maddi.