top of page

Tablets for weight loss. Review of 12 popular weight loss pills and supplements

This is a detailed, evidence-based review of the 12 most popular weight loss pills and supplements on the market today.

There are many possible solutions for weight loss.

Some options are more popular than others, including certain pills, medications, and natural supplements. They claim that they help you lose weight, or at least make the weight loss process easier if you combine them with other methods.

They typically work through one or more of these mechanisms:

  • Reduces appetite, makes you feel fuller, so you consume fewer calories;

  • Decreased absorption of nutrients such as fat, causing you to consume fewer calories;

  • Increasing fat burning so you burn more calories.

It is important to note that few of these treatments have any scientific basis, and some may have serious health consequences. You should always discuss diet or supplement changes with your doctor or registered dietitian.

To separate the myths from the facts, here are 12 of the most popular weight loss pills and supplements backed by science.

Tablets for weight loss
Tablets for weight loss

Weight loss pills and supplements

1. Garcinia cambogia extract

Garcinia Cambogia became popular worldwide after it was featured on the Dr. Oz Show in 2012. It is a small green fruit shaped like a pumpkin. The skin of the fruit contains hydroxycitric acid, the active ingredient in garcinia cambogia extract, which is sold as a diet pill.

How it works

Animal studies show that it can interfere with an enzyme that produces fat in the body and increase serotonin levels, potentially helping to reduce cravings.


In one meta-analysis, researchers examined four electronic research databases to examine the effectiveness of medicinal herbs, including garcinia cambogia.

In 54 randomized controlled trials of healthy overweight or obese adults, the authors found no difference in weight or body fat percentage between the garcinia cambogia group and the placebo group.

A 2020 review of eight trials of garcinia cambogia found that, on average, it led to about 3 pounds (1.34 kg) of weight loss.

Side effects

Although it is generally accepted that garcinia cambogia is safe to take in recommended amounts, studies conducted over the past few years have indicated some serious side effects.

A 2018 study documented four cases of women who developed acute liver failure after taking weight loss supplements containing Garcinia Cambogia.

Additionally, hepatotoxicity or liver dysfunction and some episodes of mania have also been reported in association with Garcinia Cambogia.

Summary: even though garcinia cambogia may promote moderate weight loss, the effect is quite small and may not be noticeable.

2. Hydroxycut

Hydroxycut has been around for over a decade and is one of the most popular weight loss supplements in the world.

The brand makes several products, but the most common one is simply called “Hydroxycut.”

How it works

It contains several ingredients that are claimed to help with weight loss, including caffeine and some plant extracts, such as green coffee extract, which we will talk about later.


In 2011, a meta-analysis of five clinical trials found that adding C. canephora robusta or green coffee extract, one of the key ingredients in Hydroxycut, resulted in about 5.5 pounds (2.47 kg) of weight loss compared to a placebo.

Side effects

If you are sensitive to caffeine, you may experience anxiety, nervousness, tremors, nausea, diarrhea, and irritability. Hydroxycut products were pulled from the shelves due to cardiovascular risks in 2004 and hepatotoxicity in 2009. Acute liver injury has also been associated with the use of Hydroxycut supplements.

Summary: There are few large-scale studies of this supplement and no data on its long-term effectiveness. Additional studies are needed to determine efficacy and safety.

3. Extract of green coffee beans

Green coffee beans are simply coffee beans that have not been roasted.

They contain two substances that are believed to help with weight loss: caffeine and chlorogenic acid.

How it works

Caffeine can increase fat burning, and chlorogenic acid can slow down the breakdown of carbohydrates in the gut.


Several human studies have shown that green coffee bean extract can help people lose weight. A meta-analysis of all current randomized controlled trials on the effects of green coffee bean extract on obesity found that the supplement had a significant effect on minimizing body mass index.

Other benefits

Green coffee bean extract may help lower blood sugar and blood pressure. It is also high in antioxidants.

Side effects

It can cause the same side effects as caffeine. Chlorogenic acid in coffee beans can also cause diarrhea, and some people may be allergic to green coffee beans.

Summary: Green coffee bean extract may lead to moderate weight loss, but keep in mind that many of the studies that found this were industry-sponsored.

4. Caffeine

Caffeine is the most widely used psychoactive substance in the world.

It occurs naturally in coffee, green tea, and dark chocolate, and is added to many processed foods and beverages.

Because caffeine is considered a metabolic booster, companies commonly add it to commercial weight loss supplements.

How it works

One study discussed caffeine's effect on weight regulation by increasing energy expenditure—essentially, you burn more calories through increased fat breakdown and through the body's heat production process called thermogenesis.


Some studies show that caffeine can cause moderate weight loss in humans.

Side effects

In some people, high amounts of caffeine can cause anxiety, insomnia, nervousness, irritability, nausea, diarrhea, and other symptoms. Caffeine is also addictive and can impair sleep quality.

There is no need to take supplements or pills containing caffeine. The best sources are good quality coffee and green tea, which contain antioxidants and other beneficial properties.

Summary: Caffeine can help boost metabolism and increase fat burning in the short term. However, tolerance to the effects can develop quickly.

5. Orlistat (Alli)

Orlistat is a pharmaceutical drug sold over the counter as Alli and by prescription as Xenical.

How it works

This diet pill works by preventing the breakdown of fat in the gut, meaning you get fewer calories from fat.


A 2003 meta-analysis of studies found that people who took orlistat for 12 months in combination with lifestyle changes saw a 2.9% greater weight loss than a placebo group.

Other benefits

Orlistat has been shown to slightly lower blood pressure and may reduce the risk of developing type 2 diabetes when used in conjunction with lifestyle changes.

Side effects

This drug has many digestive side effects, including loose, greasy stools; flatulence; and frequent bowel movements that are difficult to control. It can also contribute to deficiencies in fat-soluble vitamins such as A, D, E, and K.

A low-fat diet is often recommended while taking orlistat to minimize side effects. Interestingly, a low-carbohydrate diet (without medication) is thought to be as effective as orlistat and a low-fat diet combined.

Both diets were equally effective for weight loss, but showed no significant differences in blood sugar and lipid levels. However, orlistat combined with a low-fat diet was more effective in lowering blood pressure.

Summary: Orlistat, also known as Alli or Xenical, can reduce the amount of fat you absorb from food and help you lose weight. It has many side effects, some of which are very unpleasant.

6. Raspberry Ketones

Raspberry ketone is a substance found in raspberries that is responsible for its distinctive smell. A synthetic version of raspberry ketones is marketed as a weight loss supplement.

How it works

In isolated mouse fat cells, raspberry ketones increased fat breakdown and increased levels of the hormone adiponectin, which is thought to be associated with weight loss.


There is very little human research on raspberry ketones. However, one 2013 study looked at raspberry ketones and some other ingredients and found a potential 2% increase in weight loss over 8 weeks compared to a placebo.

One study in mice using high doses showed some delay in weight gain. However, high doses of raspberry ketones have also been associated with increased blood sugar levels and increased levels of ALT, a liver enzyme that indicates liver dysfunction.

It is not known whether these effects will apply to humans. More research is needed to determine the benefits and risks.

Side effects

Because of them, belching can smell like raspberries.

Summary: There is no evidence that raspberry ketones cause weight loss in humans, and the rat studies that suggest they may work used significant doses. Additional research is needed.

7. Glucomannan

Glucomannan is a type of fiber found in the roots of elephant yam, also called konjac.

How it works

Glucomannan absorbs water and becomes gel-like. It "sits" in your gut and promotes satiety, helping you eat fewer calories.


One clinical trial found that taking glucomannan for 60 days could reduce body weight among overweight participants, but only if they took the supplement consistently.

Other benefits

Glucomannan is a fiber that feeds friendly bacteria in the gut. It can also lower blood sugar, blood cholesterol and triglycerides and is effective against constipation.

Side effects

It can cause bloating, flatulence, and loose stools, and it can interfere with some oral medications if taken at the same time.

It is important to take glucomannan with a glass of water about half an hour before meals.

Summary: studies show that glucomannan fiber combined with a healthy diet can help people lose weight. It also leads to improvements in various health indicators.

8. Meratrim

Meratrim is a relative newcomer to the diet pill market. It is a combination of two plant extracts — Sphaeranthus indicus and Garcinia mangostana — that can change the metabolism of fat cells.

How it works

It claims to make it harder for fat cells to reproduce, reduce the amount of fat they take from the bloodstream, and help them burn stored fat.


There is very little research on Meratrim. One study involved 60 obese people who followed a strict 2,000-calorie diet and increased physical activity while taking Meratrim or a placebo.

After 8 weeks, the Meratrim group lost 11 pounds (5.2 kg) and 4.7 inches (11.9 cm) from their waists.

Another study found that Meratrim had a long-lasting effect on appetite suppression.

Side effects

No side effects were reported.

Summary: one study found that Meratrim caused weight loss and had a number of other health benefits. However, the study was funded by industry and more research is needed.

9. Green tea extract

Green tea extract is a popular ingredient in many weight loss supplements. That's because numerous studies have shown that the main antioxidant it contains, EGCG, can help burn fat.

How it works

Green tea extract is believed to interfere with enzymes such as pancreatic lipase, which in combination with reduced fat absorption may be an effective way to treat obesity.


Many human studies have shown that when combined with exercise, green tea extract can increase fat burning and cause fat loss, especially in the abdominal area.

Side effects

Green tea extract is usually well tolerated. It contains some caffeine and may cause symptoms in people who are sensitive to caffeine.All the health benefits of drinking green tea can also apply to green tea extract.

Summary: green tea and green tea extract may slightly increase fat burning and may help you lose belly fat.

10. Conjugated linoleic acid (CLA)

Conjugated Linoleic Acid has been a popular fat loss supplement for years.

It is known as one of the "healthier" trans fats and occurs naturally in some fatty animal products such as cheese and butter.

How it works

Conjugated linoleic acid can reduce appetite, speed up metabolism and stimulate the breakdown of fat in the body.


In a large review of 13 studies, researchers found that conjugated linoleic acid caused weight loss of about 1.1 pounds (0.52 kg) compared to a placebo. That number rises to 2.3 pounds (1.05 kg) in people over the age of 44.

According to another 2012 review, conjugated linoleic acid can make you lose about 1.5 pounds (0.7 kg) compared to a placebo. The authors conclude, questioning the clinical significance of the small effect of conjugated linoleic acid on body weight.

Side effects

Conjugated linoleic acid can cause various digestive side effects and have harmful effects in the long term, potentially contributing to fatty liver, insulin resistance, and increased inflammation.

Summary: Conjugated linoleic acid can be an effective weight loss supplement, but it can have harmful effects in the long term. The slight weight loss it might cause is not worth the risk.

11. Forskolin

Forskolin is an extract of a plant from the mint family that is considered effective for weight loss.

How it works

This can increase levels of a compound inside cells called cAMP, which can stimulate fat burning.


One study in 30 overweight or obese men found that forskolin reduced body fat and increased muscle mass without affecting body weight. Another study of 23 overweight women found no effect.

Side effects

There is minimal data on the safety of this supplement or the risk of side effects.

Summary: two small studies of forskolin have shown conflicting results. It is best to avoid this supplement until more research is done.

12. Bitter orange/synephrine

A type of orange called bitter orange contains the compound synephrine.

Synephrine is related to ephedrine, which used to be a popular ingredient in various diet pills. However, the FDA has since banned ephedrine as a weight loss ingredient due to serious side effects.

How it works

Synephrine has similar mechanisms to ephedrine, but is less potent. It can help reduce appetite and increase fat burning.


Very few studies have been done on synephrine, but many studies have found that ephedrine can cause significant short-term weight loss.

Side effects

Like ephedrine, synephrine can have serious heart-related side effects. It can also be addictive.

Summary: Synephrine is a fairly powerful stimulant and potentially effective for short-term weight loss. However, the side effects can be serious, so it should be used with extreme caution and under the supervision of a doctor.
Weighing after weight loss
Weighing after weight loss

Prescription drugs for weight loss

In addition, some prescription diet pills have proven to be quite effective.

The most common of these are Contrave and Phentermine.

According to a 2014 review, even prescription diet pills don't work as well as you might think. On average, they can help you lose 3-9% of your body weight compared to a placebo.

Remember that this is only when these pills are combined with a healthy weight loss diet. They are ineffective by themselves and are unlikely to be a useful long-term solution to obesity. They also have many possible side effects.


Of the 12 diet pills mentioned, the ones supported by the strongest evidence are:

  • Weight loss: glucomannan, conjugated linoleic acid, and orlistat (Alli);

  • Increasing fat burning: caffeine and green tea extract.

However, many medical professionals advise against orlistat due to unpleasant side effects and conjugated linoleic acid due to its harmful effects on metabolic status.

Glucomannan, green tea extract and caffeine remain. These supplements can be helpful, but the effect is modest at best. And you can find all three naturally in food and drink without resorting to supplements.

After all, no supplement or pill is effective for weight loss. They may give your metabolism a little boost and help you shed a few pounds, but that's probably where their effect ends.

Finding a healthy weight, focusing on mindful eating, using a safe calorie deficit, and increasing physical activity are still the best ways to lose weight, and these methods work better than all diet pills combined.


bottom of page