After returning to Britain, she told the media, "I used to look at myself in the mirror and cry. Now I smile and say, 'Yeah, I like myself. I like my face and I like the way my body is shaped.' The world is my oyster and I feel I can achieve anything."
But back home she felt isolated, as neither her family nor her friends were sticking to a healthy eating plan. Davis wants more help from Britain's National Health Service because her problem is no different from drug or alcohol addiction.
"I know I'm probably eating myself to death again, but at the moment I can't face up to it," she told the Daily Mail.
"I think it's unfair she got lambasted," said Keith Ayoob, director of the nutrition clinic at the Rose R. Kennedy Center at Albert Einstein College of Medicine. " It just underscores a very, very difficult problem. And it's more than addiction, because you can't quit cold turkey -- you have to eat."
"It's like someone telling you that you have to limit yourself to two drinks a day, but you have to take some," he said. "And unlike many other conditions, in obesity everybody's got an opinion they want to share with you."
Gaining and losing weight can be a "vicious cycle," according to Manuel Villacorta, a registered dietician and spokesman for the American Dietetic Association.
His Eating Free program emphasizes eating all foods, but learning how to balance food types, manage portions and to lose weight slowly.
"I don't know what [Davis'] situation was," he said. "You try to figure out what is wrong -- the environment she lives in, the lack of knowledge and confusion, lack of support, medical reasons and the big one -- the emotional component of food and its draw for her."
Hormones in the brain keep the body in a "calm, alert state" throughout the day and are inextricably tied to eating, according to Villacorta. Carbohydrates raise serotonin, which induces calm; protein raises dopamine, which triggers pleasure; and fat lowers the stress hormone cortisol, raising endorphins in the brain.
Stress and eating can cause all those hormones to kick in.
"She was getting high eating," he said.
Many Americans face the same issues with an abundance of food -- "every flavor, whatever you want in a matter of seconds," Villacorta said.
Scientists are learning that the hormone ghrelin, which stimulates appetite, helps defeat most dieters, according to Villacourta. It slows down the metabolism just when the body starts to cut back calories and begins to store fat, especially in women.
"The second you delay meals, skip meals, the body starts producing the hormone naturally," he said.
At camp, Davis was prescribed a strict 1,500-calorie diet, but may not have learned sufficiently to make better food choices.
"Sometimes, knowledge does change behavior, but someone needs to work with her on coping mechanisms so she doesn't go back to eating the drug," said Villacorta.
Wellspring Academy says that students enrolled for at least two semesters lose an average of 81 pounds.
But according to Yale University's Katz, 85 to 90 percent of all diets fail, especially among the morbidly obese.
"We are quick-fix society and people want a silver bullet," he said. "They go and sign up for the pickle juice diet, but they haven't fundamentally changed their skill power. You deprive yourself for six weeks to get to look good in the black dress for the wedding, but you can't stay lean for the long haul.
"Extreme obesity has more issues, and you have to get at the source," said Katz. "I suspect that what we are talking about in this story is self-esteem, and that may be just the tip of the iceberg."
Many who are obese need to take responsibility for themselves -- with social and emotional support.
"No one can eat and exercise for you," said Katz. "But before you ask people to take responsibility, make sure they are empowered to do it or often they fail."