For a drug to be considered effective, federal regulators like to see at least a five percent improvement over placebos. The Associated Press quotes Lazard Capital Markets analyst Terence Flynn as stating that lorcaserin appears to be "on the border of criteria recommended by the [Food and Drug Administration]." On Friday, San Diego-based Arena Pharmaceuticals -- the company that makes lorcaserin -- was up nearly 8 percent to $5.28 in late trading.

With nearly 65 percent of U.S. adults overweight and more than 30 percent obese, the obesity drug market has hefty potential. Moreover, even beyond America's borders, the rest of the world isn't getting any skinnier either. Decision Resources sees the obesity drug market rising to more than $2.7 billion in 2016 from $478 million in 2006.

Along the way, however, there have been many high profile stumbles. During the late 1990s, numerous appetite suppressant Fen Phen drugs -- named for the combination of fenfluramine and phentermine -- were recalled because of links to heart valve disease. Since then, companies and consumers have been on a quest to find a safe diet drug that really works.

Going forward, one of the challenges for lorcaserin is the fact that the drug appears to be less effective in promoting weight loss than Orexigen Therapeutics's Contrave and Vivus' Qnexa, both of which are in development after trial results earlier this year. People taking Contrave shed 8 percent of their weight, while Qnexa takers saw losses of 13 percent to 15 percent, according to the Associated Press.

For Arena's part, the biopharmaceutical company said that people who took 10 milligrams of its drug once a day lost 14.3 pounds, or 6.5 percent of their body weight. Patients who doubled the dose lost 17 pounds, or 7.9 percent of their body weight. Meantime, people who swallowed just the dummy pill actually didn't do too poorly, losing 8.7 pounds or 3.9 percent of their body weight.

Arena, of course, puts a positive spin on the results, stating that "The clinical data show lorcaserin is a solution that could provide physicians with a weight-loss medication applicable for broad use in the majority of their patients who need to lose weight and improve their health." The company goes on to point out that it will work with the FDA to prepare the drug for commercialization. This being America, the market may indeed end up determining the drug's fate.