Phentermine from Fen-phen makes up half of Qnexa. The company claims that it's the non-"toxic" half of Fen-phen that's included in the new drug.
Some doctors are wary of the medicinal approach and stress the merits of hard work, diet and exercise.
"The problem is if we start throwing multiple levers that regulate chemical pathways in the brain, there's a pretty good chance you are going to reap the whirlwind," said Dr. David Katz, director of Yale University's Prevention Research Center. "We have evolved into a quick-fix, active-ingredients, silver-bullet type of society. So, many people would rather wait for a wonder drug to come along to fix their weight control issues, than to do the hard, but more effective work of learning how to eat well, figuring out how to make physical activity a part of their daily lives."
As part of the drug study, both Evans and Dickerson changed either what they ate or how much, and they started to exercise. But an effective diet pill could make it possible for some patients to keep eating while losing weight.
Americans already spend $35 billion a year on losing weight and the drug industry is on the quest to find the next wonder drug to crack the formula for weight loss. Safe and successful weight-loss drugs stand to make billions and billions of dollars in a market starving for a solution.
"There's no doubt that the holy grail of medicine is going to be weight loss, only because all the medical problems -- diabetes, heart problems -- are all related to weight," said Fujioka. "So, if somehow we can get weight down, we correct six to 10 other major problems in the U.S."
Qnexa, the drug administered to patients in the clinical trial, has so far been reported as linked to an average weight loss of 14.7 percent in one year. Contrave's testers report an average loss of between 8.1 and 11.5 percent in their trials and Lorcaserin was linked to 8 percent of body weight.
"Our market research shows that Lorcaserin will be very successful to address the biggest need for this market, which is to allow patients to lose weight in a safe fashion and keep the weight off over a long period of time," said Jack Lief, president and CEO of Arena Pharmaceuticals, who is developing Lorcaserin.
None of the drug developers has reported serious side effects, which have typically been the Achilles heel of many drugs.
But to keep the weight off for a long period of time, some doctors say patients will likely be required to stay on the drugs for years.
"America needs to understand that when you start a weight-loss medication, you can't just start it, expect to get a kick start, and the weight comes down and you can stop it," said Fujioka. "A lot of these medications for people who are seriously overweight are long-term medications -- just like blood pressure, just like cholesterol, you're going to need to take them for years."
Qnexa, which both Evans and Dickerson took, was the drug that has reported the most dramatic results.
For Evans, it has been life-changing. Since she lost weight, her blood pressure has gone down, and her knees are no longer as strained. She attributes her weight-loss success to Qnexa.
"[Before] I swear I would get too hungry. Your body gets used to that same amount of food and your body yells at you and I obey my body," she said.