The WeightWatchers guide to weight-loss medications

It depends on the exact medication, but weight-loss medications typically work by suppressing your appetite, increasing feelings of fullness, or both. Newer ones, like GLP-1s, as well as older medications, like phentermine-topiramate and bupropion-naltrexone, target areas of the brain associated with appetite so you don’t feel as hungry. “The brain is the final common pathway for any drug that reduces appetite,” says Dr. Robert Kushner, M.D., a professor of medicine in endocrinology and medical education at Northwestern University Feinberg School of Medicine in Chicago.

While most weight-loss drugs require a prescription, there is one you can get over-the-counter.

There’s only one over-the-counter medication for weight loss that’s been approved by the FDA, and that’s Alli, a brand name of the drug orlistat. (Xenical, which has a higher amount of orlistat than Alli, is available by prescription.) Orlistat works by preventing your body from absorbing some of the fat in your diet so that it instead gets removed in your waste.

If you’ve seen other weight-loss products on the shelf at stores, they may be a waste of money at best — and at worst, dangerous to your health. ”Everything else you may be thinking about is a dietary supplement with a completely different regulation,” says Kushner. They don’t undergo the rigor of safety and efficacy testing as required by the FDA and there’s no evidence that they work.

All other weight-loss medications, including injectable GLP-1s as well as oral medications like phentermine-topiramate (known by the brand name Qsymia) and bupropion-naltrexone (known by the brand name Contrave), are only available with a prescription from a licensed provider.

They all have FDA approval, which means that the medication has gone through extensive clinical trials to assess its efficacy and safety. In other words, “the drugs have to demonstrate a certain amount of weight loss,” says Kushner.

Here’s a deeper look at all the FDA-approved options currently available, including how they work and how much weight you can expect to lose.

Semaglutide is in a category of prescription drugs called glucagon-like peptide-1 agonists, or GLP-1s, and they have upended the way obesity is treated. “The closest thing to magic today is a GLP-1,” says Dr. Peter Vash, M.D., an endocrinologist and internist in Los Angeles who specializes in obesity medicine. “They're safe and they're effective.” GLP-1s work by mimicking a naturally occurring hormone that increases insulin, thus lowering blood shower, and slows stomach emptying, which can help you feel fuller. It also targets certain appetite receptors in your brain, bringing down hunger more.

There are different drugs within the GLP-1 category, but semaglutide, which is a weekly injectable medication, is among the best known due to its large impact on weight and the fact that it was the first GLP-1 approved for weight loss. One study found that semaglutide can lead to an average 15% weight loss in a little over a year. It’s prescribed under the brand name Wegovy for weight loss and Ozempic and Rybelsus for treatment of type 2 diabetes (Rybelsus is an oral version as opposed to an injectable).

Tirzepatide works similarly to semaglutide, but in addition to mimicking GLP-1, tirzepatide also mimics the hormone GIP (which stands for glucose-dependent insulinotropic polypeptide). GIP is another gut hormone that helps your body release insulin to control blood sugar and slows digestion, thereby making you feel less hungry. Zepbound is the brand name of tirzepatide approved for weight loss, while Mounjaro is FDA-approved for treatment of type 2 diabetes. Both are given via weekly injections.


Thanks to the dual action of GIP and GLP-1, tirzepatide has been found to have a bigger impact on your weight than other prescription GLP-1s. In a study published in the New England Journal of Medicine, people lost 20.9% of their starting weight after roughly a year on tirzepatide. But “although tirzepatide kind of outpaces semaglutide in head-to-head trials, both of them are very effective,” says Kushner.

Liraglutide, which comes as a daily injection, was the first prescription GLP-1 FDA-approved for weight loss. But it’s been overshadowed in recent years by semaglutide and tirzepatide. This is because it doesn’t have the same impact on weight as the newer GLP-1s and is given daily. “Although it is approved for obesity treatment, it's not a preferred drug because it's less effective and needs to be taken daily,” Kushner says.

When people paired liraglutide with diet and exercise, liraglutide leads to an average weight loss of 5% to 10% in about a year. Similar to the other GLP-1s, there is a version approved for weight loss (Saxenda) and one for treatment of type 2 diabetes (Victoza).

The side effects vary from medication to medication, and they largely depend on the type of weight-loss drug in question. “All the GLP-1 medications share the same side-effect profile, which is mostly gastrointestinal,” says Kushner. Their common side effects include nausea, diarrhea, and constipation, although they tend to be mild to moderate when you use them properly and improve as your body gets used to the medication.

As for other medications that work directly in the brain, like phentermine-topiramate and bupropion-naltrexone, their side effects are a bit different. “Some of them can vary, but you get dry mouth, dizziness, and headache,” says Kushner. “But they tend to be mild.” Orlistat has some unique (and unpleasant) side effects, like gas, oily or loose stools, and oily spotting (since your body has to get rid of the excess fat that it's not absorbing).

For a full list of side effects for these medications, visit the manufacturer’s website or look at the packaging insert.

And we say this with our full chest: No. Weight-loss medications “are not a substitute for good dietary habits and physical activity,” says Vash. “They should be used alongside them, not as a substitute for them.” In fact, the research on weight loss for these drugs combines them with a healthier diet and increased exercise.

That’s just because of the nature of weight-loss medications, which largely work by reducing appetite. “That means that if you respond to the medication, you're going to eat less food, and therefore you're going to lose weight because you're eating fewer calories,” says Kushner. “But that does nothing for your fitness level, your muscle health, your stamina, and your strength, balance, and agility.”

Losing weight also causes you to lose muscle alongside fat — something strength training can help you with. On top of that, exercise on its own can improve cardiovascular and bone health, “so it’s never an either-or decision,” Kushner says. “It's always medication and remaining physically active and eating a healthy, balanced diet.”

That’s why WeightWatchers Clinic doesn’t just provide access to medication, but also tailored nutrition and exercise programs and one-on-one appointments with clinicians and dietitians.

As many options as there are right now, there will likely be more in the future thanks to the promising weight-loss medications on the horizon, according to Kushner. “There are dozens of medications that are in studies that will likely be approved over the coming years,” he says. These may include ones that combine other components with GLP-1, like tirzepatide does, or ones that work to mimic other gut hormones with different qualities.

The available format of existing medications may also change. “The most exciting area is the availability of oral medications and those are likely coming around the next year or two,” says Kushner. “So you'll be able to come close to reproducing what we get with a weekly injection with an oral daily medication.”

If you’re considering a weight-loss medication, there are more options out there than ever before. GLP-1s, which you inject once a week or daily, are the most effective drugs, while oral medications are more convenient and tend to cost a lot less. In general, the FDA-approved medications have mild side effects that tend to get better with time. To see the biggest health improvements, combine any weight-loss medication with regular exercise and a healthy diet. Ultimately, your provider at WeightWatchers Clinic can help determine the right weight-loss medication for you.