“You burn fewer calories and it makes it easier to gain more weight, which becomes a vicious cycle,” Charlton said.

In the long run, high blood sugar levels can damage blood vessels’ walls, leading to kidney, eye, brain and heart damage. Obesity also leads to the buildup of fat cells in the arteries, blocking blood and oxygen to organs.

“We used to think that fat was just fat and stayed there and it didn’t look very pretty,” said Dr. Tracie Miller, associate chair of Pediatrics for Clinical Research at the University of Miami Health System.

But fat cells secrete inflammation signals that lead to the production of white blood cells. It all accumulates in the arteries, blocking the flow of the blood to the organs, leading to oxygen deficiency.

“I cannot think of one organ that is not affected from obesity,” Miller said. “There’s a tremendous association between childhood obesity and adult complications. It’s like an accelerated aging process.”

She said while it is not likely that heart attacks would start happening in teenagers, people who were obese as children and as adults may get a heart attack in their 30s and 40s.

When it comes to healthy eating, the number of calories is not that important, said Charlton. But the quality of the calories is — a piece of fruit is far better than a pack of fruit roll-ups.

“With fruit you are getting a lot of vitamins and minerals. And you will also get fiber and give your body the micronutrients to function properly,” he said.

Miller targets two behaviors in her patients: consumption of soda and mindless eating, such as munching on snacks while watching TV or working on the computer.

“It’s OK to eat a box of cookies. But sit down at the dining room table to do it,” she said. “You have to sit down and think about what you are doing.’’

With Type 2 diabetes, exercising helps by making cells more sensitive to insulin flowing in the bloodstream. The result: A person does not need that much insulin and the body no longer stores calories.

“The primary benefit of exercise is that it changes how you burn calories for hours afterwards because you become more sensitive to insulin,” Charlton said.

The sooner the problem is targeted, the better.

When Daniella Friedman’s son, River, gained 20 pounds in the past year and a half, she took him to a pediatrician. It was just in time as his cholesterol levels were on the border of being too high.

He started the nutritional portion of the Crunchtime program in March. Over the summer he went three days a week to customized fitness classes.

“They helped me learn the healthiest way to eat, so I switched to wholewheat for a lot of things and I added calcium to my diet,” said 12-year-old River Friedman, his curly blonde hair bouncing as he walked on the treadmill at the Batchelor Children’s Research Institute in Miami. “I’ve cut out all the junk food. I learned to not really like them.”

He went from weighing 127 pounds to 125 – not a dramatic weight loss. But that is not the point of Crunchtime.

“Even if we don’t have a change in weight, we have a big influence on the type of tissue there is in the body,” said Gabriel Somarriba, an assistant professor and a physical therapist at UM’s Division of Pediatric Clinical Research.

Pediatricians can measure a child’s body composition – loss of adipose tissue, or body fat, versus gain of lean mass – to determine if the program is working.

Like many other children, River gained weight through no fault of his own. He was on a prescription migraine medication that lowered his metabolism and increased his appetite. Other kids may have genetics issues.

“If you are just genetically one of those people who gains weight easily, then that is not a situation you can change,” Charlton said. “We struggle with kids all the time who are working really hard and still are struggling. There’s nothing fair about that.”

But many of the cases of overweight and obese children can be attributed to unhealthy lifestyles: Too many calories, too little exercise.

Last summer, Miami-Dade Parks’ Fit-to-Play program joined with Fitzness International’s Morning Mile initiative, where children run or walk a mile every morning. The program started in Gainesville and has spread throughout Florida and Texas.

“I feel better. I have more energy,” said Moises after he finished his mile around the track at Hammocks Community Park.

Added Chelsea: “I lost a lot of weight so I don’t have to wear baggy clothes. I could wear the clothes that I really wanted.”