5 FDA-Approved Prescription Weight Loss Pills That Really Work

Updated: Feb. 09, 2021

In recent years, the FDA has approved five prescription weight loss pills for long-term use. None of these weight loss pills are magic bullets, and all work best in conjunction with lifestyle changes including a healthy diet and regular exercise.

Illustration of a pill bottle and pills.
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Lorcaserin (Belviq)

As with all these drugs, it’s approved by the FDA for people who are obese—they have a body mass index (BMI) greater than 30 (for example, someone who is 5’6″ would have to weigh more than 185 pounds); or for people who have a BMI greater than 27 (such as a 5’6″ person who weighs 167 or more) with an obesity-related condition such as type 2 diabetes, sleep apnea, high blood pressure or high cholesterol. Most of these drugs should only be taken short-term and in conjunction with counseling from a medical provider. See how to calculate your BMI.

Lorcaserin (Belviq) is a medication that stimulates the area of the brain that regulates appetite and satiety, explains Scott Kahan, MD, the director of the National Center for Weight and Wellness in Washington, DC. Belviq takes aim at the brain receptors for serotonin, a brain chemical that plays a role satiety. (Serotonin also plays a role in mood regulation.)

What can you expect? Studies comprising nearly 8,000 obese and overweight people who took Belviq show that 37.5 to 47.5 percent of patients lost more than 5 percent of their body weight over a one-to-two-year period. Patients also made diet and exercise modifications. His rule of thumb is that if you do not lose 5 percent of your weight after 12 weeks of treatment, you likely will not respond. “We are seeing good weight loss in about 50 percent of patients and it is very safe,” he says. Both cholesterol and blood sugar levels also seem to decrease among Belviq users. Side effects may include headache, dizziness, fatigue, nausea, dry mouth, constipation, and low blood sugar for people who take drugs to treat diabetes, but there is a very low likelihood of these, he says. It is among the best weight loss pills when it comes to safety. “One of the feathers in Belviq’s hat is that it is very well tolerated,” he says. That said, people with a history of heart disease, psychiatric disorders and those who are pregnant should not take this medication. The FDA’s advisory panel initially rejected this weight loss pill due to risk of tumors seen in animal studies, and the European Medicines Agency was so concerned about the drug’s safety that it rejected Belviq. However, an analysis in JAMA indicates that Belviq is linked to fewer adverse events than other Rx weight loss pills. Try these 50 ways to lose weight without a lick of exercise.

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Liraglutide (Saxenda)

Approved in 2014, Saxenda stands out from the Rx weight loss pill pack because it is the only one given as shot. It is a higher dose of an older diabetes drug called Victoza. Saxenda mimics the effects of GLP-1, 1 (glucagon-like peptide), a hormone made in the intestines, that curbs appetite.

What can you expect? Study participants who ate a reduced-calorie diet, increased their exercise regimen and took Saxenda lost an average of 18 and a half pounds over 56 weeks, according to findings published in the New England Journal of Medicine. By contrast, those who made these lifestyle changes, but received a placebo instead of Saxenda lost just six pounds. “I have seen great results with Saxenda especially in patients at risk for diabetes and those who have a family history of diabetes,” says Reshmi Srinath, MD, assistant professor of Diabetes, Endocrinology, and Bone Disease at the Icahn School of Medicine at Mount Sinai in New York City. To know whether you’re at risk, check to see if you have these habits that raise your chances of developing type 2 diabetes. Saxenda side effects may include nausea, which can be severe, vomiting, diarrhea, constipation and/or low blood sugar, Dr. Kahan says.

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Naltrexone SR/Bupropion SR (Contrave)

Contrave is a combo of two older medications at specialized dose combinations. Naltrexone SR has been approved to treat opioid use and alcohol use disorders, while bupropion helps with smoking cessation and depression.

What can you expect? “The two cause little, if any, weight loss by themselves, but together there is a synergistic weight loss effect of about 13.5 percent in responders,” Dr. Kahan says. Taken twice a day, this drug can reduce cravings and can be particularly effective in people who have food addictions. “This has not been fully studied and can’t be promoted as such but it may have better effects for people who have addictive personalities.” Side effects include nausea, but it’s usually mild and goes away in about two weeks. “In 4 percent of people, however, it is not so mild and doesn’t go away so we stop the medication,” Dr. Kahan says.

Illustration of pill bottle with orlistat capsules.
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Orlistat (Rx: Xenical; OTC: Alli)

This is the only weight loss pill that works by blocking the absorption of fat, says Caroline Apovian, MD, professor of medicine and pediatrics in the Section of Endocrinology, Diabetes, and Nutrition at Boston University School of Medicine. She’s also the new president of The Obesity Society. It’s one of the older approved drugs and is available in prescription and over-the counter strengths; Alli, the OTC version, is half the dose of the prescription strength.

What can you expect? “When combined with good counseling, it can be extremely helpful and result in 10 to 15 percent weight loss or more in those who respond,” Dr. Kahan says. It can be hard to determine who these super responders are in advance. “We do have very striking data showing that people who respond in the first three months are likely to keep responding at least through one year, and those who don’t likely won’t lose any more weight after that,” he says. It is taken three times a day with meals, and can cause fatty diarrhea especially after of high-fat meals, which makes it hard for some people to continue. Anyone who takes this medication should also take a multivitamin because this weight loss pill can deplete essential vitamins while blocking fat absorption. People who are pregnant or have other malabsorption problems should not take this medication, he says.

Illustration of Qsymia bottle and capsules.
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Phentermine/topiramate ER (Qsymia)

Qsymia is another combination weight loss pill. “It’s a small dose of phentermine combined with topiramate, an anti-seizure and migraine drug,” Dr. Apovian says. If phentermine sounds familiar, it is likely because it was part of the once-popular, now controversial weight loss pill duo known as Fen/Phen. The fenfluramine part was pulled from the market in Sept. 1997 after it was linked to potentially fatal heart valve problems.

What can you expect? “You only get moderate weight loss with phentermine by itself, but when it is combined with topiramate, we see much more weight loss and this weight loss is durable,” Dr. Kahan says. In fact, the JAMA analysis found that it was the best weight loss pill for women and men when it comes to the amount of weight lost. On average, participants who took Qsymia lost just short of 20 pounds after a year. “Response should be evaluated after 12 weeks, and treatment should either be escalated to a higher dose or discontinued if a person has not achieved a 3 percent or more weight loss,” Dr. Kahan says. Qsymia is not recommended for people with glaucoma, overactive thyroid glands and those who take certain antidepressants due to risk of serious eye problems, increased heart rate and/or suicidal thoughts or actions. A note about phentermine: “It is still on the market, very inexpensive and highly prescribed on its own,” Dr. Apovian says. It is only approved for short-term weight loss, and it can worsen anxiety. There are also three other weight loss pills that are FDA-approved for short-term use—benzphetamine, diethylpropion, and phendimetrazine.

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Important points about weight loss pills

Medical weight loss treatment is offered to all patients with obesity who have a BMI greater than 30 with or without complications and those with BMI is 27 or greater with obesity-related complications. “They must have sufficient excess weight that affects their health and have tried more conservative measures to lose weight and been unable to lose weight or keep it off,” Dr. Apovian says.

Illustration of a plateful of diet medications.
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Weight loss pills—the big picture

In broad strokes, “you can expect a 5 to 8 percent weight loss, on average, over six months, and you will lose more when you take these medications in conjunction with a diet and lifestyle program,” adds Dr. Srinath. “People who chart and monitor their calories and exercise also tend to lose more weight,” she says.

Illustration of the weight loss medications.
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Decisions, decisions

There is no algorithm that says this person will do better on this weight loss pill, but there are ways to whittle down the choices. “This starts with a thorough evaluation that takes other health conditions, medication use, allergies, and lifestyle factors into account,” Dr. Srinath says. Many of the weight loss pills interact with other medications or conditions, so this typically eliminates several choices. Cost is also a big issue, Dr. Apovian adds. These medications can be prohibitively expensive, costing hundreds of dollars a month and they aren’t always covered by insurance, she says. Discover what your doctor wishes you knew about weight loss.