"The new drugs seem safe, but so did the Fen-phen combo," he said.
Many experts, including Ayoob, said it is safe to assume that there will be side effects with these drugs.
"Any drug powerful enough to cause weight loss is probably going to cause other problems," said Dr. Sidney Wolfe, director of Public Citizen's Health Research Group based in Washington, D.C.
"It is difficult to believe the risk of memory loss and other neurological effects found with topimarate will provide adequate safe use," said Dr. George L. Blackburn, associate director of nutrition at Harvard Medical School.
Blackburn said if the drugs do end up on the market, they will target those who are obese and possibly morbidly obese.
"Studies have looked at the morbidly obese -- about 7 percent of our population falls into this category -- that's a group that has a huge need," said Fujioka.
Though risky, invasive procedures such as gastric bypass surgery clearly offer better results than taking diet pills. But many obese Americans may not qualify for surgery.
Fujioka predicted that pills may eventually be as effective as gastric banding.
"Candidates for bariatric surgery will become candidates for these medications," he said.
Given the grim history of many diet pills that have come and gone, many experts said they don't think the answer to the obesity epidemic can be found in a pill.
"The more effective drugs are less safe, and the safer drugs are less effective," said Katz. "[More than half] of overweight adults [are] metabolically healthy. Why would we put metabolically healthy people on a drug when they don't need it?"
Regardless of whether a person undergoes surgery or takes diet pills, both options must be accompanied by an overall healthier lifestyle that includes diet and exercise, according to ABC News' Senior Health and Medical Editor, Dr. Richard Besser.