For the first time in 13 years, the Food and Drug Administration (FDA) has approved new medications for long-term weight management. In the U.S., more than one-third of adults are obese. Achieving and maintaining a healthy weight can reduce the risk of potentially serious health problems that can stem from obesity.

The new drugs, marketed as Belviq and Qsymia, are approved for patients 18 years and older whose body mass index (BMI) is 30 or greater. Adults with BMI of 27 or greater may qualify if they have at least one additional weight-related condition.

Potential patients can calculate their BMI online at www.nhlbisupport.com/bmi/. Generally, adults with a BMI of 30 or higher are considered obese.

Both Belviq and Qsymia are intended for use along with diet and exercise. They must be prescribed by and used under a physician’s supervision, since both carry potentially serious side effects.

Belviq works by activating a serotonin receptor in the brain that affects satiety or the amount of food eaten during a meal. Taken twice daily, it may help patients feel fuller and, as a result, eat less. In clinical trials that included nearly 8,000 obese and overweight patients, average weight loss ranged from 3 percent to 3.7 percent. Patients who combine the drug with diet and exercise are likely to lose more weight. If patients do not lose 5 percent of their weight after 12 weeks of treatment, further use is likely to be ineffective and they should stop taking it.

While past weight loss drugs such as Fen-Phen posed risks of heart valve problems, studies of Belviq to date have shown no such issues. However, patients with existing heart valve disease or congestive heart failure should consult their physician as Belviq may not be appropriate. Additional studies are planned to study whether Belviq affects the risk of heart attack or stroke.

Diabetes patients should be closely followed by their physicians while using Belviq. As they lose weight, their diabetes will improve and blood sugar levels can get dangerously low. Patients taking certain depression medications should not use Belviq because of potential drug interactions.

Qsymia, taken once daily, combines two FDA-approved drugs: phentermine, an appetite suppressant, and topiramate, an anti-seizure medication. In clinical trials with Qsymia the average patient lost between 6.7 percent and nearly 9 percent, depending on the dose taken. Like Belviq, Qsymia is meant to be used with diet and exercise to obtain maximum weight loss. If patients have not lost at least 5 percent of their weight after 24 weeks on the highest dose, Qsymia should be gradually discontinued by their doctor.

Women should not become pregnant while taking Qsymia because of an increased risk of birth defects such as a cleft lip or cleft palate. It is still unknown if Qsymia is safe for patients with cardiovascular disease.

Dr. Ken Fujioka specializes in weight management, metabolism and diabetes at Scripps Clinic.