A U.S. Food and Drug Administration Advisory Committee today recommended approval of the weight loss drug Qnexa, a treatment many hope will help millions of Americans who struggle with obesity .

In voting  20 to 2 for approval, the committee said today that Qnexa's weight loss benefits for the chronically obese outweighed the risks of birth defects and cardiovascular problems that have been associated with the drug. An FDA advisory panel recommended against approval in 2010 over concerns about the drug's side effects, and the FDA rejected it shortly after that. Vivus, the drug's manufacturer, recently submitted additional research.

The committee today recommended that the manufacturer take a number of steps to prevent the drug from causing birth defects like cleft palate, including a possible warning label targeted toward women of childbearing years.

The FDA has considered numerous anti-obesity drugs in the past 20 years, but most have failed to meet the agency's standards for safety and effectiveness. But so far, data on Qnexa suggests that the drug is the most effective in helping patients shed up to 10 percent of their body weight. Those changes, along with diet and exercise modifications, could go a long way toward alleviating some of the health problems associated with obesity, such as diabetes and high blood pressure.

The FDA is expected to decide whether or not to approve Qnexa by April 17. The agency usually follows the recommendations of its advisory panels but is not required to do so.

Critics say the risk of potentially dangerous side effects of Qnexa, which include increased heart rate, heart attacks and arrhythmias, are too great to make the drug available to millions of people, especially because long-term effects of the drug are still largely unknown.

"Public health cannot tolerate another diet drug approved that has not been accepted for cardiovascular risk especially in light of the suggested findings of Qnexa," said Dr. Sidney Wolfe, director of the health research group at Public Citizen, an advocacy group.

Obesity currently plagues one-third of Americans and has been linked to high blood pressure, diabetes and a range of other chronic, expensive health problems. Doctors and dietitians routinely recommend changes in diet and exercise as the safest and most effective way to shed pounds. But some acknowledge that these strategies just don't work for a large number of obese patients. Bariatric surgery, though largely successful in producing weight loss, is not a viable option for many people.

Dr. Melina Jampolis, an obesity specialist in San Francisco, said the current options for treating obesity are "frustratingly limited," and said it would be helpful if patients had additional tools to aid their weight loss.

"I think that combination therapy is essential as there are numerous individual and overlapping mechanisms that make weight loss difficult," she said. "So the more of them that you can address with medication therapy when necessary, the more effective a regimen will be."