Do weight-loss pills work?

Weight-loss pills. The phrase smacks of diet-culture from the era of late-night infomercials. But a new generation of medications to treat obesity has taken hold on TikTok and other social media. And these new drugs are backed by actual science and prescribed by actual doctors. But do they live up to their hype in real life? We tapped a few experts for their take on what weight-loss medications can and can't do.

How weight-loss pills work

Weight-management medications work by either making you less hungry—they reduce cravings and increase feelings of fullness—or by decreasing the body’s ability to absorb and store fat from food. Some do this by affecting hormone levels, which can slow down how fast your body digests food and keep you full for longer. Others target areas in the brain associated with hunger and rewards, making you crave food less and reducing your calorie intake. The one outlier is orlistat, which blocks how much fat you absorb when you eat (the unabsorbed fat is then passed out of your body when you go to the bathroom).

Are all weight-loss pills created equal?

There are two main groups of weight-management medications: those you get through a healthcare provider (prescription weight-management medications) and those you buy without a prescription (supplements, including diet pills). There’s a canyon of a difference between them.

Dietary weight-loss supplements and diet pills (the kind you get without a prescription) have been around for decades, but they aren’t regulated by the FDA, meaning they aren’t tested for safety or efficacy. This counts for so-called natural supplements that claim to rev your metabolism. (Think raspberry ketones and apple cider vinegar pills.) And the same is true for more clinical-seeming ones that contain ingredients with strong biological effects. Take Hydroxycut. This popular supplement, which touted celebrity spokespeople and sleek magazine ads, was pulled from shelves in 2009 after numerous reports of liver damage and even death.

Now, on the complete other side of the universe—we’re talking a galaxy far, far away—are what’s known as weight-management medications, which need to prove that they’re safe and work well to be approved by the FDA, and are only available via prescription. What’s more, they exist to treat an actual chronic health condition—like obesity—not to simply help someone shed a few pounds.

“We are getting a better understanding of the complex factors that influence obesity,” says Dr. Diana M. Plata, M.D., an obesity and sleep medicine physician for Northwest Community Healthcare in Arlington Heights, Illinois. “More importantly, the treatment options are expanding, which is very encouraging to those living with obesity.”

Are weight-loss pills safe?

This comes down to what you’re referring to: FDA-approved prescription medication or over-the-counter pill. To get FDA approval, drugs have to go through rigorous safety and efficacy testing, with any possible dangers or risks included on the packaging. The same is not true for other pills you may find on the shelves. Over-the-counter weight-loss supplements aren't necessarily evaluated for anything by anyone, meaning you don't really know what's in the bottle — or how your body will react to it.

10 medications FDA-approved for weight loss

While the following medications—which include both pills and injections—have been put through the paces research-wise, they aren’t a magic cure for everyone, and many come with side effects.

Short-term medications and how they work:

The FDA has approved the following four drugs for short-term use because they are stimulants classified as schedule III or IV drugs and may lead to dependency. They all work in a similar way, revving up the central nervous system to suppress appetite:

• Phendimetrazine (Bontril)
• Diethylpropion (Tenuate)
• Benzphetamine (Didrex)
• Phentermine (Adipex-P, Fastin)

Long-term medications and how they work:

• Orlistat (Xenical, Alli) is a gastrointestinal lipase inhibitor, meaning it stops your body from absorbing the fat in your food.
• Phentermine/topiramate (Qsymia) is a stimulant combined with an anti-seizure medicine that suppresses appetite by calming excitable nerve cells in the brain.
• Naltrexone/bupropion (Contrave) combines an antidepressant (Bupropion) which suppresses appetite with hormone-impacting Naltrexone to help control food cravings.

• Liraglutide (Saxenda) is a synthetic version of a hormone, known as glucagon-like-peptide (GLP-1), that is naturally found in your body and increases feeling of fullness.
• Semaglutide (Wegovy) is a once-a-week injection that curbs appetite and delays gastric emptying so you feel fuller for longer.
• Tirzepatide (Zepbound) is a once-a-week injection combining GLP-1 with gastric inhibitory polypeptide (GIP) to reduce appetite and food noise.

Some antidepressant, diabetes, and anti-seizure medicines are occasionally prescribed to possibly promote weight loss. This is considered an “off-label” purpose, meaning for another use than originally designed.

What do you need to know about weight-management pills and medications?

1. They can work. Studies have shown that people who take weight-management medications tend to lose weight from the start, says Dr. Robert F. Kushner, M.D., a professor of medicine and medical education at Northwestern University Feinberg School of Medicine and Medical Director of the Wellness Institute at Northwestern Memorial Hospital in Chicago. The rate of weight loss will vary from one person to another, but research has found that you can expect to lose about 5% to 15% of your weight in the first six months of treatment.
   
   
2. They don’t work alone. Experts overwhelmingly recommend the use of these medications together with a lifestyle modification program, like WeightWatchers, which focuses on eating a healthier diet, exercise, and behavior change techniques. This helps promote optimal weight management and overall health over the short- and long-term. WeightWatchers also has a GLP-1 Companion Program, designed to help those taking GLP-1s make lifestyle changes and feel their best while losing weight.
   
   
3. They can improve your health. While 5% weight loss might not seem like a lot—this means 10 pounds for someone who weighs 200 pounds—research links this amount of weight loss to a lower risk for diabetes, healthier cholesterol levels, less chronic inflammation, and more. (Here’s what 5% looks like on bodies of different sizes.)
   
   
4. They require regular check-ups. Also know that you aren’t just prescribed a weight-management medication and sent on your way. You’re seen regularly by your doctor and after three months of treatment, your healthcare provider will likely review your progress to determine whether you’re responding to the medication, Kushner says. "If not, we may stop the medication and consider an alternative medicine or approach.”

Who is a candidate for weight-management medications?

Most healthcare providers consider the use of weight-loss medications if your weight is impacting your health. The medication will be prescribed in combination with a program like WeightWatchers that encourages behavior changes such as eating differently and increasing physical activity. As a general rule, weight-management medications might be an option if:

You have a body mass index (BMI) of 30+

You have a BMI of 27+ as well as certain qualifying health conditions, such as high blood pressure, type 2 diabetes, or sleep apnea

Body mass index (BMI), by the way, is one way to get a general idea of excess weight by looking at a person’s weight in kilograms divided by the square of height in meters. A “healthy” weight is defined as a BMI of >18.5 to 24.9. “Overweight” is defined as a BMI between 25 to 29.9, and “obesity” kicks in at 30. (Find your BMI here.) Since BMI does not account for muscle mass, doesn’t distinguish health risks between men and women or different ethnicities and races, and overlooks other important health markers like blood sugars and cholesterol, it’s a far-from-perfect measurement system. But it’s the standard, so it’s what medical professionals use for now to screen for obesity and start the conversation.

In nearly all cases, regardless of BMI, young kids and pregnant people should steer clear of all weight-loss medications since clinical trials do not include these populations, and as such, scientists cannot validate their safety.

To talk with a healthcare provider about whether or not you're a candidate for weight-loss medications (and, if you qualify, get prescribed one), join WeightWatchers Clinic. You'll have a team of trained clinicians and get tailored nutrition plans, help navigating insurance, and more.

How long do people take weight-management medications?

Obesity is a chronic disease, and like diabetes and hypertension, it requires lifelong management. With the exception of phentermine, phendimetrazine, diethylpropion, and benzphetamine, weight-management medications are FDA-approved for long-term use, as they help address a dysfunction of the weight regulation system.

“All of the effects of the medication—like reduced hunger, increased fullness, or less cravings—are likely to return once the medication is stopped,” says Kushner. As a result, research shows that when the medications are stopped, weight regain occurs.

So, even after you've reached—and maintained—your health and weight goals, it’s important to discuss your individual situation with your healthcare provider before stopping your medication.

The truth about popular weight-loss pills

When it comes to non-FDA-approved weight-loss pills, there always seems to be a latest-and-greatest option that sounds too good to be true. It probably is. For example, Hydroxycut claimed to help you burn fat, but the product contained a stimulant ephedra and was linked to liver damage and pulled from the shelves. (You can still find Hydroxycut products out there, but they no longer contain ephedra.) Caffeine pills are another popular option, but it’s possible to take in too much caffeine, which can be dangerous to your health (and there’s no FDA oversight to guarantee how much caffeine is in any of the pills out there). Even things that sound super healthy, like green tea extract, can cause gastrointestinal issues and nausea, so are best left on the shelves. Talk with your doctor or clinician before taking any diet pills or supplements.

Bottom line

While supplements and over-the-counter weight loss pills aren’t likely effective or safe, FDA-approved medication can be helpful for people who fit the criteria. And they can work.

Think of weight-management medication as one step on a staircase that leads to long-term weight loss and maintenance. Weight loss can be challenging, but these medications help support the changes you are making in your life for a healthy you.

To find the most success, you’ll need to combine a weight-management medication with a healthy lifestyle, including regular activity, a balanced diet, stress management, healthy sleep habits, and social support. WeightWatchers can help you by offering accountability and guidance along the way.