"Obesity threatens the overall well-being of patients and is a major public health concern," Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in a statement. "The approval of this drug, used responsibly in combination with a healthy diet and lifestyle, provides a treatment option for Americans who are obese or are overweight and have at least one weight-related comorbid condition."
The drug, made by Arena Pharmaceuticals, acts on a receptor in the brain to help people eat less and feel fuller, according to the FDA statement.
In clinical trials people who took Belviq were twice as likely to lose 5 percent or more of their weight than people who took a placebo. The drug was also linked to improvements in blood pressure, cholesterol and blood sugar levels.
"It's about time that they approved a new drug," said Dr. Judith Stern, a professor of nutrition at the University of California at Davis. "Obesity drugs should be on the fast track."
In 2010, the FDA decided not to approve Belviq, citing concerns that the drug carried heart-valve risks and increased brain and breast tumor development in rats given seven times the recommended dose.
But new studies by Arena Pharmaceuticals found no increased risk of heart valve problems and only a small risk of cancer. And in May 2012, an FDA panel voted 18 to four to approve the drug, stating the benefits of Belviq outweigh the potential risks when used in a population of overweight and obese people.
"For the half of America that seriously needs some help in reducing energy intake, this has some promise," said Dr. Barry Popkin, a professor of nutrition at the University of North Carolina at Chapel Hill. Other experts have expressed more caution.
"The approval of [Belviq is] a foot in the door for pharmacological treatment of obesity," said Dr. Robert Eckel, a professor of medicine at the University of Colorado -- Denver. "However, the effects are moderate at best."
Obesity is becoming an epidemic of massive proportions. According to the World Health Organization, by 2015 2.3 billion adults will be overweight, and more than 700 million will be obese. Obesity is associated with a host of health problems, including high blood pressure, diabetes, heart attacks, asthma, cancers and strokes. Indeed, obesity, along with tobacco, is a leading cause of preventable death.
The main treatments for obesity are diet and exercise. If those interventions are not effective, then a person can consider medical therapy or bariatric surgery. However, bariatric surgery, though effective in leading to weight loss, is also a surgical procedure with serious risks.
"Clearly [Belviq] is only effective in some cases, but clinicians who deal with very obese and super obese Americans are dying for an increased arsenal other than bariatric surgery," said Popkin.
The most common side effects of Belviq are headache, nausea and dizziness. And people taking Belviq were twice as likely to have neuropsychiatric and cognitive side effects.
Weight-loss drugs have a mixed track record with the FDA. Fenfluramine -- commonly known as fen-phen -- was pulled from the market in 1997 because of its association with heart valve disease. Accutrim was removed in 2000 because of its association with strokes. And Meridia production ceased in 2010 due to concerns of heart disease and strokes.
Only one weight-loss medication, Alli, was FDA-approved before today's decision.