Do weight-loss pills work?

In this article:

1/ Over-the-counter weight-loss supplements vs. prescription weight-loss pills

2/ Are weight-loss pills safe?

3/ Do prescription weight-loss pills actually work?

4/ How do weight-loss pills work?

5/ Types of weight-loss pills

6/ Who is a candidate for weight-loss pills?

7/ How long do you take a weight-loss pill?

8/ The bottom line

“Weight-loss pills.” The phrase smacks of diet-culture from the era of late-night infomercials — especially now that we’re firmly in the age of injections for weight loss. But while there are always going to be pills touted on TikTok and other social media as the next best thing, there are also legitimate FDA-approved oral weight-loss medications that are backed by actual science and prescribed by actual healthcare providers. But how effective are these FDA-approved options? We tapped a few experts for their take on if prescription weight-loss pills work. Here’s a look at the options available and what you need to know.

Over-the-counter weight-loss pills vs. prescription weight-loss pills

There are two main groups of weight-loss pills: those you get through a healthcare provider and those you don’t.

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.

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 prescription 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.

Are weight-loss pills safe?

This comes down to what you’re referring to: an FDA-approved prescription medication or an over-the-counter pill. To get FDA approval, prescription 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 diet pills aren't necessarily evaluated for anything by anyone, much less the FDA, meaning you don't really know what's in the bottle — or how your body will react to it. And some can have very serious health consequences, like liver damage or heart trouble.

That said, even if a prescription weight-loss pill has been tested in clinical trials and approved by the FDA, it can still come with certain side effects and risks — GI issues, for example. Your healthcare provider should review these with you during your consultation, says Dr. Diana M. Plata, M.D., an obesity and sleep medicine physician for Northwest Community Healthcare in Arlington Heights, Illinois.

Do prescription weight-loss pills actually work?

Studies have shown that prescription weight-loss pills are effective at helping people lose weight. The rate of weight loss will vary from one person to another and depends on what medication you choose, but research has found that you can expect to lose around 5% of your weight or more on them.

While 5% weight loss might not seem like a lot — it’s less than the 15% to 20% average weight loss you can experience on injectable GLP-1s like Wegovy — 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.)

That said, prescription weight-loss pills are meant to be combined with a lifestyle program, like WeightWatchers, which focuses on eating a healthier diet, getting more exercise, and other behavior-change techniques. This helps promote optimal weight and overall health over the short and long term.

How do weight-loss pills work?

Prescription weight-loss pills typically work by making you less hungry. Some do this by controlling cravings or keeping you full longer after you eat. Others target areas in the brain associated with hunger and rewards. 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).

Types of weight-loss pills

The FDA has approved a handful of prescription weight-loss pills, with new GLP-1 options (such as Rybelsus) likely getting approved in the not-so-distant future. “We are getting a better understanding of the complex factors that influence obesity,” says Plata. “More importantly, the treatment options are expanding, which is very encouraging to those living with obesity.” Here’s what’s available today:

Appetite suppressants

As the name implies, these pills make you less hungry, reducing how many calories you take in to help you lose weight. There are two approved by the FDA:

• Qsymia (phentermine/topiramate) is a combination of two medications: phentermine, which reduces appetite, and topiramate, which is used to treat seizures and migraines. It helps curb hunger and make people feel full sooner, which often results in eating less. Two large trials conducted in 2012 found that after one year of treatment, people on Qsymia lost significantly more weight than participants who took a placebo, with an average weight loss of around 10%.
  
  
• Contrave (naltrexone/bupropion) combines an antidepressant (bupropion) which suppresses appetite with hormone-impacting naltrexone to help control food cravings. In a clinical trial of more than 1,700 men and women, which was sponsored by the drug’s manufacturer, those taking Contrave lost 5.4% of their body weight on average over the 56 weeks they were tracked. In a randomized controlled trial conducted by WeightWatchers, patients lost an average of 4.2% of their body weight at 12 weeks when they combined the medications with the WeightWatchers behavioral program, which equated to 54% more weight loss than those who were on the medications alone. This highlights the importance of a behavior change program alongside prescription weight loss pills.

Fat absorption inhibitors

The main player here is orlistat, which is prescribed as Xenical or available over the counter as Alli. It’s a gastrointestinal lipase inhibitor, meaning it stops your body from absorbing the fat in your food. As a result, the remaining fat is eliminated from the body during bowel movements. In a six-month study published in the Journal of Obesity, participants who took Xenical lost, on average, over 9 pounds. When combined with diet and lifestyle changes, you could lose up to 10% of your weight on orlistat. And another study found that, compared to placebo, orlistat led to a significant reduction in weight along with waist circumference, total cholesterol, and LDL (“bad” cholesterol) levels.

Short-term appetite suppressants

The FDA has approved 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 and increase energy expenditure. The most commonly prescribed one is phentermine, with three others that are prescribed less frequently: phendimetrazine, diethylpropion, and benzphetamine.

Who is a candidate for weight-loss pills?

Most healthcare providers consider the use of weight-loss medication — pills or injections — if your weight is impacting your health. While injections are the newest options, some people may prefer a pill if they don’t like the idea of using a needle on themselves or if the GLP-1 injections result in severe side effects that impact their quality of life.

Either way, 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, 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 pills or other medications (and, if you qualify, get prescribed one), join WeightWatchers. You'll have a team of trained clinicians and get tailored nutrition plans, help navigating insurance, and more.

How long do you take a weight-loss pill?

Obesity is a chronic disease, and like diabetes and hypertension, it requires lifelong management. With the exception of phentermine, phendimetrazine, diethylpropion, and benzphetamine, weight-loss pills 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 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. As a result, research shows that when the weight-loss 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 bottom line

While supplements and over-the-counter weight-loss pills aren’t likely effective or safe, FDA-approved weight-loss pills can be helpful for people who fit the criteria. And they can work, with some resulting in a 5% weight loss or more. Think of weight-loss pills 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.