5 FDA-Approved & Scientifically Proven Weight Loss Medications

Scientifically Proven Weight Loss Medications

Losing weight is tough, as anyone who has tried to do so can attest to. Exercise and calorie restrictions leave people hungry and exhausted. To these individuals, anything that can speed up the process of losing weight is a welcome aspect of the weight loss process, especially when it is something as small and simple as a diet pill.

In 2015 alone, Americans spent $2 billion on weight-loss supplements, even though the diet pill industry has had some questionable historical tidings.1

In the diet pill realm, there are two primary categories: over-the-counter supplements and prescription drugs. These are vastly different in their composition and the level of regulation.

The following are some essential aspects to know about each type as well as how effective they are in helping you lose weight.

FDA-Approved Weight Loss Medications (Prescriptions)

There are 5 FDA approved prescription medications available for long-term weight reduction (listed below in alphabetical order). These approvals are based on their efficacy and safety:

1. Liraglutide (Saxenda)

Saxenda Obesity Science & Practice published the finding of five trials in their 2017 review that showed that those participants who took liraglutide lost 5% to 10% of their body weight versus those who were given the placebo.2

Some participants did drop out of the trials after experiencing multiple side-effects including nausea and vomiting.

2. Naltrexone-bupropion (Contrave)

Contrave While bupropion and naltrexone are two separate drugs, research has linked a higher efficacy in consuming both of them in terms of weight loss to be superior to either consumed individually.3

It is important to know, however, that the studies for this weight loss medication were sponsored by the drug’s producer.

3. Orlistat (Xenical/Alli)

Xenical Studies indicated that an average of 12.3 lbs can be lost by those with a BMI of 27 kg/m or more while taking this drug.4

An interesting aspect of a 2012 study, however, found that soldiers that consumed orlistat for half a year lost less lean mass, but more body mass than the study’s placebo taking participant group.

4. Phentermine (Adipex)

Adipex A study show that more than 45% of the patients who took phentermine lost about 5% of their body weight.5

Phentermine first became FDA-approved in 1959, as an appetite suppressant for short-term weight management. A decade later, Phentermine’s hydrochloric salt entered circulation. King Pharmaceuticals used to sell it as Fastin on behalf of SmithKline Beecham until 1998, when it lost market authorization.

5. Phentermine-topiramate (Qsymia)

Qsymia Of the five approved medications for weight loss, this one seems to be the most effective. In a study by Lancet in 2011, almost half of the participants who took a pill with 15 mg of phentermine and 92 mg of topiramate daily for 56 weeks were able to drop 10% of their total body weight.6

There are some side effects associated with this medication that include insomnia, constipation, and dysgeusia (warped sense of taste).

Some drugs outside of the above list (like phentermine) are only approved for short term use. However, it’s important to note that medication geared at weight-loss is not for everyone.

Such treatments are often reserved by physicians only for patients with a BMI more than 30 kg/m or those who have health complications like diabetes or high blood pressure related to obesity.

These medications are not really a good solution to obesity on their own. They are typically used in tandem with a regular exercise regimen and a healthy diet, both things that need to continue after the medication treatment is done. That is before even mentioning the often common and at times, severe, side effects.

Nonprescription Weight Loss Supplements

According to the FDA, dietary supplements, which are not prescribed medications, do not require FDA approvals ahead of marketing. Because weight-loss supplements are not heavily regulated by the FDA, acquiring them is much easier.7

This also means that many of the dietary supplement pill manufacturers often will not test the pill via human trials before releasing them to the market.8

Having said that, if you have been thinking about taking a dietary supplement, there are some things to keep in mind.

Also read: Most Effective Over-the-Counter Alternatives to Phentermine Diet Pills.

Diet pills have content that includes herbs, enzymes, vitamins, and minerals, with most of the common ingredients available to be found in the National Institutes of Health database.

This database stores all known information about a particular ingredient that is currently known including its safety and efficacy.

Consider Garcinia cambogia that is included in products like Plexus Slim and Hydroxycut.

Its purpose is to lessen the number of fat cells produced by your body and suppress your appetite, but while it is rated as moderately safe, excessive consumption of this particulate has been found to be linked to issues with the liver.9

Chitosan, a component of some other diet pills comes from shrimp, crab, and lobster shells, and while theoretically, it binds fat in the digestive tract preventing it from being absorbed by the body, according to NIH, the fat content it binds is unlikely to be enough to help shed any significant weight amounts.10

In a 2019 study, for instance, it was observed that rats who were given caffeine lost more weight than those that were not. There is however no correlation to suggest that this would have a similar effect on humans.11

Other ingredients like yerba mate, guarana, bitter orange, and caffeine are common in weight loss supplements, but there is not much data that points to them actually promoting significant weight loss.

That Which Sounds Too Good To Be True, Probably Is

While the dietary supplement ingredients should promote weight loss in theory, determining if they actually do so is hard to determine.

When you take diet pills full of multiple ingredients, it’s with the assumption that you are already observing a calorie-restrictive diet, making it hard to distinguish whether the weight loss was a result of the lower calorie intake or if the supplements assisted in the matter.

It is important to talk to your pharmacist regardless of which diet pills you consider trying out. This is doubly important if you are taking any other medications.

Many of the ingredients are considered safe on their own, but can have detrimental or toxic effects when consuming in high doses. In fact, some of them are safe on their own but may interact with other medications with very undesirable results.

A pharmacist can help you reconcile any potential interactions and alert you of any red flags depending on your medication consumption.


  1. Household expenditures on dietary supplements sold for weight loss, muscle building, and sexual function: Disproportionate burden by gender and income.
  2. Liraglutide for weight management: a critical review of the evidence.
  3. Naltrexone HCI/bupropion HCI for chronic weight management in obese adults: patient selection and perspectives.
  4. Orlistat.
  5. Effects on Weight Reduction and Safety of Short-Term Phentermine Administration in Korean Obese People.
  6. Effects of low-dose, controlled-release, phentermine plus topiramate combination on weight and associated comorbidities in overweight and obese adults (CONQUER): a randomised, placebo-controlled, phase 3 trial.
  7. FDA 101: Dietary Supplements.
  8. Dietary Supplements for Weight Loss; Fact Sheet for Consumers.
  9. Garcinia cambogia (Hydroxycitric Acid) as a Potential Antiobesity Agent – A Randomized Controlled Trial.
  10. Chitosan supplementation and fat absorption in men and women.
  11. Caffeine enhances activity thermogenesis and energy expenditure in rats.

Last updated: Jan 21, 2021. Bookmark the permalink.

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