Back in New York, Lori Cohen was putting Dolgoff's program to the test, introducing Samantha to new "green light" foods. As Cohen saw it, helping Samantha to lose weight was about more than just the physical. She too had been heavy as a little girl, she said, and suffered years of hurtful teasing.
"I don't want her getting hurt, I don't want her to lose that self-esteem," Cohen said. "I want her to go and reach the stars."
Two weeks into the program, they saw results: Samantha had lost one pound.
But it wasn't all good news. Dolgoff had results from Samantha's physical exam. They showed abnormally high levels of cholesterol.
For Cohen, it was further confirmation that she was doing the right thing.
To take the program a step further, Samantha and her mom joined Dolgoff and her daughter for a "Mommy & Me" workout with a fitness trainer.
At her next check-up two weeks later, Samantha had maintained her weight and grown a quarter of an inch.
"The important thing for kids is maintaining the weight while also growing, so she is doing great," Dolgoff said.
Back in Tennessee, Nick was working on his new healthy goals. He played basketball with his brother while, back in the kitchen, his mom helped him with portion control.
"We show Nicholas how to look for a serving size," said Reeves, placing snacks in single servings into plastic bags.
Reeves was introducing vegetables to snack on. "He has learned that mac and cheese is not a vegetable," she said.
And every other day, Reeves and Nicholas went on walk-jogs around the neighborhood.
"We're training for a 5K in September," Reeves said.
"This is the fourth week that we did it," Nick said. "And it gets easier every time."
"Nightline" checked in with Cohen and Samantha to see how things were going nearly six months into their program.
"She understands if food is a green, it's healthy, if it's a yellow, not so good, and if it's a red that's a once-in-a-while thing," Cohen said.
Cohen showed us some of the changes she had made in the kitchen, which was stocked with butter spread, low-cal vitamin water and after-school snacks of fruit and cheese.
"Broccoli was a hit, spinach was a hit," Cohen said. "Tonight we're going to try artichokes. And we're going to try some pre-seasoned salmon burgers, because she asked for hamburgers tonight."
A big lesson for Cohen has been learning how to set boundaries.
"Second helpings are a no," she said. "I tell her that it's not healthy, 'How would you like some fruit, how would you like a banana?'"
But is it really feasible for children so young to stick to such new routines ?
In two months, Nick's BMI had actually become slightly worse: He gained five pounds while not growing a single inch taller.
"I think this points out that even with a supportive family and tools that we give families, it really is hard to lose weight," Plemmons said.
Nick's mother said they would continue the battle at home. "I know he is more healthy with the exercise and the food choices that he's making and his attitude. ... I'm a very proud mom," Reeves said. "Very proud mom."
In six months, Samantha's BMI was down.
"She is out of the obese category, she's in the 93rd percentile," Dolgoff said. "She did almost lose three pounds, and that's equivalent to an adult losing 15 to 20 pounds."
"It's fantastic," Cohen said. "It's exactly what I wanted to have happen."