ABC News' Linsey Davis and Liz Sintay report:
Marika Stone tipped the scale in January at 250 pounds. She wore size-20 pants, and they were tight on her.
Stone, of Connecticut, was 56 pounds lighter last week, and she credits that success - and her new size-12 figure - to a program called Medi-Weightloss, a chain of diet clinics supervised by doctors and registered nurses.
The company says its multipronged approach, which includes counseling, vitamin shots and, in some cases, appetite suppressants, has been so successful in curbing appetites that its more than 172,000 thousand patients have lost 2.5 million pounds since the chain opened in 2006.
The Florida-based company has more than 75 centers in 21 states.
New patients are given a physical and put on a reduced-calorie diet that is typically 500 to 700 calories of protein, plus 200 to 400 calories in fruits, vegetables and healthy fats.
By comparison, the U.S. Department of Agriculture's recommended calorie range for a moderately active middle-aged woman is 2,000 calories a day.
Medi-Weightloss suggests certain vitamins and supplements, depending on an individual's needs, and advises them to come in for weekly checkups of their weight and vital signs. Appetite suppressants are recommended for some patients.
"What they do is we want them to help them be comfortable when they're on a lower calorie diet," nurse practitioner Jill Tanner of Medi-Weightloss said. "So it helps decrease their appetite while they're on this."
Asked whether the program was safe, Tanner replied: "Yes. Yes."
The average cost of the program is $39 per pound of weight lost.
The supplements and the low-calorie, high-protein diet are intended to put the body into a state called ketosis, in which the body is tricked into believing it needs to burn its fat to survive, thereby inducing weight loss.
Dr. Louis Aronne, director of the Weight Control Program at New York-Presbyterian Hospital/Weill Cornell Medical Center in New York City, who has been researching and treating obesity for over 20 years, said ketosis can "activate the body in ways that make you think there is an emergency going on."
"We don't think that being in ketosis for a long period of time is a good thing," said Aronne, who is not affiliated with Medi-Weightloss.
Medi-Weightloss says ketosis is used only in the "acute" phase of its plan and typically would not be used for more than 12 weeks, which even Dr. Aronne says might be a reasonable option for the dangerously obese.
Allure magazine featured the clinics in its July issue.
Kristin Perrotta, executive editor for Allure, said Medi-Weightloss is merging the kind of traditional strip-mall diet center, such as Jenny Craig or Weight Watchers, with the kind of medically supervised diets that have typically been available to people of privilege.
Stone says Medi-Weightloss hasn't changed her life; it's become a way of life, and she's counting on shedding more weight. Her goal weight is 160 pounds.