Weight Loss Medications: Are They Effective?

Craig Primack MD

Reviewed by Craig Primack, MD, FACP, FAAP, FOMA

Written by Rachel Sacks

Published 01/04/2024

There’s a reason why healthcare professionals may recommend weight loss prescription drugs, and it’s not just about achieving a certain look. It’s because on average, those who take medications as part of a weight management plan lose up to 12 percent more of their starting body weight than people who don’t.

There are plenty of FDA-approved weight loss drugs these days. But do they actually work or is it all hype? And which one is the best? Below, we’ll take a look at the best weight loss medications and how effective they really are.

Which Medications Are FDA Approved for Weight Loss?

It’s common knowledge that managing your weight keeps you healthy now and as you get older. In fact, obesity contributes to several health conditions, including heart disease, stroke, type 2 diabetes and certain types of cancer.

Not only was the prevalence of obesity in U.S. adults nearly 42 percent in 2017, but the estimated medical costs for adults with obesity were almost $2,000 more each year than for adults who do not have obesity .

Those who have a body mass index (BMI, or the measurement of fat based on height and weight) between 25 and 30 are considered overweight, while those with a BMI over 30 are considered to have obesity.

You’ve probably heard of a few weight loss medications, or at least their brand names, like Ozempic® and Wegovy®. However, there are several other prescription drugs available that are approved by the U.S. Food and Drug Administration (FDA) and frequently prescribed off-label for weight loss.

Healthcare providers may prescribe these medications to someone who has obesity or is overweight with a weight-related health problem like high blood pressure, high cholesterol or diabetes.

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Semaglutide (Ozempic, Wegovy, Rybelsus)

You’re probably familiar with one of semaglutide’s brand names, Ozempic — other brand names for this drug include Wegovy and Rybelsus®.

Ozempic is approved by the FDA to treat type 2 diabetes and may be prescribed off-label for weight loss, in combination with lifestyle changes like diet and exercise or with other diabetes medications like insulin or metformin.

Wegovy, meanwhile, is a prescription medication approved for use for weight loss in people who have obesity or who are overweight.

Ozempic and Wegovy are in a class of medication called GLP-1 receptor agonists, which mimic the hormone glucagon-like peptide-1 and target areas of the brain that regulate appetite.

Ozempic was approved by the FDA in 2017, while Wegovy was granted approval to pharmaceutical company Novo Nordisk more recently, in 2021.

Metformin

Although only approved by the FDA to treat diabetes, metformin is often used off-label for weight loss, as well as gestational diabetes (a type of diabetes that develops during pregnancy) and polycystic ovary syndrome (PCOS).

It isn’t exactly clear how metformin helps people lose weight, but researchers think the drug works as an appetite suppressant. Similarly to Ozempic, metformin may increase how much GLP-1 hormone your body makes. This can send a signal to your brain that you’re full, which means you eat fewer calories.

Read our blog to learn about Ozempic vs. Metformin for weight loss.

Naltrexone-bupropion (Contrave®)

If you’ve dealt with depression or looked into medication to quit smoking, bupropion may sound familiar to you.

For weight loss, it can be combined with the drug naltrexone, which is used to treat alcohol and drug dependence, to curb your hunger or make you feel fuller sooner. Together, these medications work on two areas of the brain, the hunger center and the reward system, to reduce appetite and help control cravings.

Along with a reduced calorie diet and exercise plan, naltrexone-bupropion can also help keep excess weight off.

Phentermine-topiramate (Qsymia®)

Phentermine-topiramate is actually two separate medications that are combined in Qsymia, but are offered separately in other applications. 

While phentermine is considered an anorectic and topiramate is an anticonvulsant, both help with appetite suppression.

Topiramate offers the added benefit of helping you feel fuller longer after you eat.

When used specifically with a healthy exercise regimen and a reduced calorie diet, these medications — either together or separately — have been shown to help people lose weight and keep it off.

Orlistat (Xenical®, Alli®)

Orlistat, which belongs to a class of medications known as lipase inhibitors, reduces the amount of fat your body absorbs from the food you eat.

Orlistat is used for weight loss in conjunction with exercise and a reduced-calorie diet, as well as after weight loss to help people keep from gaining back that weight.

While the brand name Xenical requires a prescription, another brand called Alli is available in a lower dosage without one.

Liraglutide (Saxenda®)

Like Ozempic and Wegovy, liraglutide is an injected weight loss medication. It works as a GLP-1 receptor agonist to suppress appetite, similarly to semaglutide.

Also available under the brand name Victoza at a lower dose, this drug is FDA-approved to treat type 2 diabetes.

How Effective Are Weight Loss Medications?

These weight loss drugs are all available with a prescription from a healthcare professional, but how effective are they really?

  • One study found that when people without diabetes took a weekly semaglutide injection they had a higher average weight loss — almost a 15 percent average decrease in weight — than people who took a placebo.

  • Metformin has also demonstrated clinically significant weight loss. A 2020 meta-analysis of 21 trials testing metformin found the drug had a modest impact on lowering BMI, especially for those who are considered to have obesity.

  • A smaller study on metformin also found that the average amount of weight lost in 154 patients was between 5.6 and 7 kgs (that’s roughly between 13 and 15 pounds).

It’s also worth mentioning cost here — if you can’t afford the drug you need to take, it’s effectiveness essentially drops to zero percent. That said, there’s some wide price disparity between weight loss drugs. 

For instance, injectibals like Ozempic and Wegovy are generally more expensive than orals like metformin — namely because metformin is a generic medication that’s been around for decades, and Ozempic and Wegovy are newer. 

How Quickly Do Weight Loss Medications Work?

Because everyone’s weight loss journey is different, weight loss medications may work slowly for some people and faster for others.

How long you need to take a weight loss prescription drug depends on various factors such as what side effects you experience, how much weight you need to lose, whether the drug helps keep the weight off and more.

Generally, as found in the studies noted above and clinical trials, weight loss will occur within the first few months of using the medication.

Sometimes your health care professional may recommend long-term use of the medication, while other people may be advised to stop the drug if they don’t lose a certain amount of weight after 12 weeks.

If you’re taking a weight loss medication, your healthcare provider will likely suggest that you also increase your physical activity and make healthy lifestyle changes like eating lots of protein and fiber and getting enough sleep. These medications are the most effective when combined with healthy habits.

Side Effects of Medication for Weight Loss

Just like any medication, weight loss drugs also come with the possibility of side effects.

When it comes to injectibal drugs like Ozempic and Wegovy, there are some broad side effects that apply to all injectibals — like swelling, redness or other discomfort at the injection site — but generally, the side effects profiles of these drugs are similar regardless of delivery method.

The most common side effects of many of these weight loss medications include:

  • Stomach pain or constipation

  • Diarrhea

  • Nausea

  • Vomiting

Some, like liraglutide and naltrexone-bupropion, may cause an increased heart rate or headaches.

Liraglutide and semaglutide may also increase the risk of pancreatitis (swelling of the pancreas). You may also have a higher risk of developing tumors or thyroid cancer when using liraglutide or semaglutide, although these serious side effects are very rare.

The Verdict on Weight Loss Medication

There’s a good chance you’ve heard of weight loss medications like Ozempic or even Wegovy, but there’s also a good chance that the headlines and celebrity-focused articles didn’t answer all your questions. Here’s what you need to know about whether they’re effective.

  • There are several FDA-approved weight loss drugs, including semaglutide, orlistat, phentermine-topiramate, naltrexone-bupropion and liraglutide. Metformin is another common medication used off-label for weight management.

  • These drugs all work slightly differently, but many decrease your appetite and help you stick to a lower-calorie diet. Healthcare providers often recommend they be used alongside regular exercise and healthy habits to maximize sustained weight loss.

  • However, there are side effects such as nausea, vomiting, diarrhea and constipation and, for the injectibals, injection-side irritation, injury or discomfort. Often, these are mild and serious side effects rarely happen.

  • Cost is also worth considering. Injectibals like Ozempic and Wegovy can generally cost anywhere from $800 to $1,000 per prescription, where a generic like metformin can be had for a fraction of that — usually for under $100 a month.

There’s no one “best weight loss medication” — there’s only what’s best for your particular needs. If you’re curious about medication for weight loss, you can talk to your healthcare provider for medical advice and to explore your options. And if you’re interested in other weight loss treatments online, we can help. 

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Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

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This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Craig Primack, MD, FACP, FAAP, FOMA

Dr. Craig Primack MD, FACP, FAAP, FOMA is a physician specializing in obesity medicine.

He completed his undergraduate studies at the University of Illinois and subsequently attended medical school at Loyola University — The Stritch School of Medicine. 

He completed a combined residency in Internal Medicine and in Pediatrics at Banner University- Phoenix, and Phoenix Children's Hospital. He received post-residency training in Obesity Medicine and is one of about 7,000 physicians in the U.S. certified by the American Board of Obesity Medicine.

In 2006, Dr. Primack co-founded Scottdale Weight Loss Center in Scottsdale, Arizona, where he began practicing full-time obesity medicine. Scottsdale Weight Loss Center has grown since then to six obesity medicine clinicians in four locations around the greater Phoenix Metropolitan area.

From 2019–2021, he served as president of the Obesity Medicine Association (OMA), a society of over 5,000 clinicians dedicated to clinical obesity medicine. He has been on the OMA board since 2010, currently serving as ex-officio trustee.

Dr. Primack routinely does media interviews regarding weight loss and regularly speaks around the country educating medical professionals about weight loss and obesity care. He is co-author of the book, “Chasing Diets.”

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