These 5 Weight-Loss Drugs Really Work—but Heres What Else You Need to Know  

If the term "weight-loss drug" kind of scares the crap out of you, we hear ya. It’s smart to be wary of gimmicky pills that promise a six-pack by the weekend. But unlike the stash of weight-loss supplements at your local drugstore, weight-loss meds prescribed by doctors have undergone years of testing to snag a seal of approval from the Food and Drug Administration.

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A recent study published in the Journal of the American Medical Association pinned five FDA-blessed medications against one another to test for their legitimacy. Researchers looked at 28 randomized clinical trials of nearly 30,000 overweight adults (yep, that's pretty solid). They found that, on average, each drug helped people lose 5 percent of their body weight after one year (about 10 pounds for a 200-pound person). All of the meds were equally effective.

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Here, we break down the five drugs that were studied, and explain what you need to keep in mind before seeking out an Rx.

Orlistat
How it works: Orlistat falls under the umbrella of medications called lipase inhibitors. Essentially, the medication prevents your intestines from absorbing some of the fat coming through your system. You might recognize orlistat by the brand name Alli, which was approved for over-the-counter sales in 2007.

Side effects: Eating high-fat meals (think: 30 percent of the calories come from fat) while taking the medication could lead to some nasty side effects. Think: oily spots on your underwear, loose stools, and urgent needs to hit the bathroom. Ick. (Get a jump start on your weight-loss journey without gross consequences with Women's Health's Look Better Naked workout DVD.)

Who could take it: Orlistat works best for people who need to lose less than 10 percent of their body weight, says Allen Rader, M.D., of Idaho Weight Loss. According to the National Institutes of Health, it’s also safe for people who have high blood pressure, diabetes, high cholesterol, or heart disease.

Naltrexone and Bupropion
How it works: “Naltrexone is an opioid inhibitor, and bupropion is an antidepressant,” says Rader. Bupropion on its own can decrease feelings of hunger, but the medication also increases certain opioids in the brain that block satiety (a.k.a. you'll never feel full). But when bupropion joins forces with naltrexone, it blocks the stimulation of these opioids and the appetite-suppressing magic occurs.

Side effects: Nausea is a major side effect of naltrexone, says Rader. “It’s hard to be hungry when you feel sick, so it helps with hunger in that manner,” he says. Not surprisingly, the medication also has a high dropout rate (maybe because people don't want to feel like yacking all the time?). Another red flag: Bupropion can lead to an uptick in suicidal thoughts for young people, according to the makers of Contrave, the brand name of these two meds.

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Who could take it: Contrave works best for people with a BMI of 30 or higher (a marker of obesity) or people with a BMI of at least 27 who also have weight-related medical problems, like high blood pressure or diabetes. Got a history of seizures or anorexia? Steer clear, warn researchers from SUNY Upstate Medical University.

Lorcaserin
How it works: According to the National Institutes of Health, lorcaserin, which is available by the brand name Belviq, works as a serotonin receptor agonist. Translation: It makes you feel full faster. When paired with a low-calorie diet and exercise, it generally helps people lose weight within three months.

Side effects: While you take it, you may deal with headaches, dizziness, and fatigue, says Rader. Another downside is that the medication helps with weight control only if you continue to take it. So once you cut it out, you could see the pounds creep back on.

Who could take it: Though lorcaserin is a derivative of the appetite suppressant fenfluramine, which was banned for causing heart problems, it doesn’t cause cardiac issues. So it’s a good choice for people who can’t tolerate the stimulant side effects of other meds, like a racing heartbeat and jitters, says Rader.

Phentermine and Topiramate
How it works: Phentermine belongs to a group of appetite-decreasing meds called anorectics, and topiramate promotes feelings of fullness to keep you satisfied long after you eat, according to the National Institutes of Health. And when you're not as hungry, you eat less (at least in theory).

Side effects: “The major side effects are stimulation from the phentermine and confusion and sleepiness from the topiramate,” says Rader. Also, topiramate has been known to increase the risk of birth defects, so it shouldn’t be taken if you’re trying to get pregnant or already are.

Who could take it: The brand Qsymia contains a combination of the two medications. Like Contrave, it’s meant for adults with a BMI of 30 or higher who’ve tried to lose weight but end up feeling frustrated and hungry all the time. Adults with a BMI of 27 or greater plus a weight-related health issue, like high cholesterol or diabetes, could also be eligible. The researchers behind the Journal of the American Medical Association study found that people taking phentermine-topiramate lost the most weight, roughly 19.4 pounds after one year.

Liraglutide
How it works: “Liraglutide was initially developed to help with the treatment of diabetes,” says Rader. But when patients using the drug unexpectedly started to lose weight, researchers developed a form of liraglutide specifically approved for weight loss.

The med works to control your blood sugar by increasing insulin release and suppressing glucagon, which leads to decreased sugar released by the liver, says Rader. It also slows the stomach-emptying process to help control hunger. A Journal of the American Medical Association study noted that it helps people achieve weight loss “by reducing appetite and caloric intake, rather than increasing energy expenditure.”

Side effects: Uneasy around needles? This injected medication might not be for you. On top of that, it's expensive and can cause life-threatening pancreatitis, says Rader.

Who could take it: Similar to other medications on the list, Saxenda, the brand name of liraglutide, is recommended for people whose BMIs qualify as obese (30 or higher) and have had trouble losing weight in the past.

The bottom line is that no weight-loss med comes free of risky side effects. So make sure you know what you're getting into before you start trying to lose weight with the help of prescription drugs. 

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