For the first time in more than a decade, the Food and Drug Administration has approved an anti-obesity drug: Belviq, a new appetite-suppressing pill, was cleared earlier this week (even though the feds initially rejected the drug in 2010 due to safety concerns). Here's what you need to know:

How does it work?
The medicine coaxes the brain into releasing serotonin, a chemical which can suppress appetite by helping people feel full faster, and also appears to give patients a metabolism boost. (Though serotonin is also a key factor in the treatment of depression, Belviq is designed to seek out only those serotonin receptors that affect appetite, says Alice Park at TIME.) Belviq, known generically as lorcaserin, is taken twice a day, and patients are urged to incorporate the drug as part of a healthy diet and exercise program approved by their doctor.

Who should take Belviq?
The FDA approved the drug for obese adults with a body mass index (BMI) of 30 or more, as well as overweight people with a BMI of 27 or more who also have a weight-related health condition, such as Type 2 diabetes or high blood pressure. 

How effective is it?
Clinical studies have shown that the drug can lead to "moderate weight loss," says the Associated Press. For example, trial data submitted to the FDA demonstrated that nearly half of all overweight test-subjects with Type 2 diabetes lost at least 5 percent of their starting weight, or an average of 12 pounds over the course of a year. (By contrast, only 23 percent of people taking a placebo lost that much.) 

What are the side effects?
Potential risks include depression, migraines, and memory lapses. The drug was rejected in 2010 over concerns that it might trigger heart-valve problems, says Park at TIME.

Is the FDA hesitant to approve anti-obesity drugs?
Yes. The last such pill to be approved was Xenical in 1999. And in the past, diet pills have been plagued by safety problems and recalls. A similar serotonin-based drug, fenfluramine, was recalled in 1997, and another weight loss drug, sold as Meridia, was removed from the market in 2010 — in both cases, over fears that the drugs posed cardiological risks.

Then why was Belviq approved?
More than 35 percent of Americans are now considered obese, a three-fold increase from 50 years ago. Belviq was given the green light after its maker convinced the FDA that, at the low doses at which it will be prescribed, Belviq won't cause heart trouble.

Sources: Associated Press, Forbes, Medical News Today, NPR, TIME