The drug, called Contrave, shows promise for the 26 percent of Americans who are obese and the 23 million Americans who have type-2 diabetes.
The manufacturers of the drug say the average patient who takes the drug for 12 months can expect to lose between 18 and 25 pounds.
In the recent trials, after 56 weeks, more than half reported weight loss of at least 5 percent, an average of over 17 pounds.
"This is not a drug for weight loss. This is a drug for the treatment of a serious condition, obesity," said Mike Narachi, president and CEO of Orexigen.
Contrave is actually a combination of two drugs: naltrexone, which is currently used to treat alcohol and drug addiction, and bupropion, an antidepressant. It's a heavy-duty drug cocktail and some weight loss experts have strong concerns about it.
The FDA just recently asked for a black box warning on bupropion because of an increase in suicidal thinking in patients taking it for depression.