Best Thermogenic Ingredients to Burn Fat — or Are They Too Risky?

You’ve likely seen the bottles for thermogenic supplements at the drugstore. They feature trim, slim men and women, flexing in bathing suits. The labels and advertisements are usually similar: lose pounds in days, build muscle quickly or other drastic results with these fat burners.

During a weight-loss plateau, you might even have been tempted to try these “miracle pills” yourself. However, the ingredients of thermogenic supplements must be scrutinized, as certain ones can be dangerous. Meanwhile, there are other, more natural ways to lose weight, such as consuming fat-burning foods.

What Are Thermogenics?

Thermogenic supplements are dietary supplements that rely on a concept called thermogenesis to promote fat loss in the body. Thermogenesis, simply put, is the production of heat. Thermogenic supplements increase heat production in the body so body fat is used as energy instead of fat.

Manufacturers claim that the supplements boost metabolism, suppress your appetite so you eat less throughout the day and encourage weight loss quickly, helping you lose those pounds faster after hitting the gym.

The active ingredients in thermogenic supplements vary by brand, but most contain a cocktail of stimulants like caffeine, guarana, green tea extract, garcinia cambogia and others. While some of these ingredients are “natural” — for example, caffeine is often included in the form of yerba mate or guarana — the amounts they’re used in can be considered unhealthy.

Interestingly enough, dietary supplements are not regulated by the Food and Drug Administration (FDA). They’re not considered drugs and, instead, are treated like special foods. So while every drug sold in the U.S., whether it’s prescription or not, must be proven safe and effective before it’s allowed on the market, thermogenic supplements don’t have to meet the same requirements.

Currently, drugs in the U.S. are treated as unsafe until proven; in the case of supplements, it’s the exact opposite. Thermogenics are considered safe until proven otherwise. Manufacturers don’t have to test their ingredients or pills in clinical trials, which could determine unsafe interactions with other medications.

The FDA does have the authority to force a company to stop selling a particular supplement — after the FDA proves the product poses a serious health risk. You read that correctly — it’s not until a significant amount of Americans have had an adverse reaction to a supplement that the FDA can begin to take action.

Ephedra, or ephedrine, was one such thermogenic supplement that was finally prohibited by the FDA because of many consumers getting sick or worse from it. In 2004, the FDA issued a disclaimer prohibiting the sale of dietary supplements containing ephedrine alkaloids because they presented “an unreasonable risk of illness or injury.”

However, because these supplements are self-prescribed and not under doctor supervision, there’s also no organized system for people who wish to report their side effects or bad reactions.

And when it comes to thermogenics, there can be many side effects if, again, you’re going with a product that contains some of the above ingredients.

Common Thermogenic Ingredients

While thermogenic supplements are brand-based, they use a variety of active thermogenic ingredients in order to supposedly increase heat production in the body so body fat is used as energy instead of fat.

Here are some of the most popular ingredients:

1. Caffeine

Caffeine is a compound that acts as a central nervous stimulant, increasing energy levels and alertness while helping to fight off fatigue. It’s found naturally in many food sources, including coffee, tea and cacao seeds. It’s also added to other products like soda and energy drinks as well.

Caffeine pills, on the other hand, are a type of supplement made using caffeine, either extracted from natural sources or manufactured synthetically. Like other supplements such as green coffee bean extract, guarana or coffee fruit, people typically use it as a quick and convenient way to take advantage of the unique health benefits associated with caffeine. In fact, research shows that caffeine consumption may help reduce the risk of depression, boost metabolism and even improve exercise performance.

Keep in mind that caffeine pills are different from caffeine powder, a supplement that the Federal Drug Administration has classified as dangerous and unlawful.

2. Guarana

Guarana is a type of climbing plant that is native to the Amazon. This plant is prized for the seeds from its powerful fruit. The seeds are very high in caffeine. They are often used as an additive in energy drink. Because of the guarana seed caffeine content, the seeds may come with other health benefits besides boosting energy levels.

In addition to fighting physical fatigue, some research indicates that guarana can help reduce mental fatigue as well. One study published in the journal Appetite showed that taking it was able to decrease mental fatigue associated with sustained mental effort in participants.

3. Green Tea Extract

According to some research findings, consuming antioxidants found in green tea, especially catechins and the compound called EGCG, may promote metabolic health and modestly prevent weight gain.

When 11 studies and articles were included in one 2009 meta-analysis that was published in the International Journal of Obesity, researchers found that “catechins or an epigallocatechin gallate (EGCG)-caffeine mixture have a small positive effect on weight loss and weight maintenance.”

4. Garcinia Cambogia

Garcinia cambogia is a tropical fruit, also known as the Malabar tamarind, that appears in popular weight-loss supplements. Supposedly, it prevents your body from making fat while stalling your appetite.

The key active ingredient found in the rind of garcinia cambogia fruit is hydroxycitric acid (HCA), which some research suggests can help certain people lose weight.

Is garcinia cambogia safe to take? What are the side effects of garcinia that can potentially occur? According to the National Center for Complimentary and Integrative Medicine, “Cases of liver damage associated with the use of garcinia cambogia products have been reported. This problem appears to be uncommon, but some cases were severe.”

While some people claim they don’t experience any side effects at all from using garcinia cambogia, others have had very different experiences. It can easily be overused and is not very well-regulated. Some manufacturers recommend taking high doses multiple times per day, for example 30 to 60 minutes before every meal, for eight to 12 weeks straight, which can wind up causing toxicity.

5. Yohimbine

Yohimbe (or yohimbine) is an herbal supplement. It is often sold in capsule or tablet form and goes by many names depending on how it’s sold.

Yohimbine may have certain fat-burning abilities and work even better while someone is fasting. Given that yohimbine can act as a mild stimulant, researchers have looked at whether it can help increase energy levels in those looking to become more active, or whether it has positive effects on reducing appetite, regulating blood sugar levels, or promoting growth of muscle mass that can then help with weight loss.

Although not every study has shown that yohimbe can have slimming effects, certain other studies have found positive results. One study found that yohimbine significantly increased mean weight loss in overweight female patients following a low-energy diet.

Possible mechanisms of action include: boosting lipolysis (the breakdown of fats and other lipids by releasing fatty acids into the blood) both during and following exercise, regulating insulin secretion, and reducing appetite.

Yohimbe also may act as a mild hallucinogenic, causing neurological reactions that can be wide-ranging. According to the Pavia Poison Control Center in Italy, “Yohimbine is currently approved in the U.S. for erectile dysfunction but has undergone resurgence in street use as an aphrodisiac and mild hallucinogen.”

6. Cayenne Pepper

Cayenne pepper (and its molecular compound found capsaicin) is a shrub that originated in Central and South America and now grows in subtropical and tropical climates. Its hollow fruit grows into long pods that turn red, orange or yellow when they ripen.

A study published in PloS One noted that consuming cayenne pepper for breakfast creates less appetite, so people eat less calories during the day. It also burns excess fat because it’s a metabolic booster. As one of the key anti-inflammatory foods, cayenne pepper benefits also include weight loss.

7. Forskolin

Extracted from the plant Coleus forskohlii, forskolin is a chemical compound that’s been used for centuries in various forms of natural medicine.

In recent years, forskolin supplements have been used to promote weight loss. There have been very few reputable studies regarding forskolin and its impact on weight loss in humans.

The first human research investigating the effects of forskolin on weight loss was conducted in 2005 at the University of Kansas and involved 30 overweight or obese men.  This 12-week study involved each man taking either a placebo or 250 milligrams of a 10 percent forskolin extract orally two times each day. It found forskolin to have a positive impact on body composition, decreasing body fat percentage and fat mass.

Later that year, a second human study conducted at Baylor University that was published in the Journal of the International Society of Sports Nutrition was conducted with 23 mildly overweight women. They were given the same dosage as the men in the first study, also for a 12-week period.

Unlike the first study, researchers found “no significant differences in fat mass or fat free mass,” meaning that body composition was not affected. In addition, no significant differences were found in any metabolic markers or blood lipids (such as increased testosterone found in the first study).

They did postulate that forskolin seemed to prevent the development of new fat mass. They found that the subjects taking it reported less fatigue, hunger and fullness.

8. Raspberry Ketones

Raspberry ketones are chemicals from red raspberries that are used for their flavor and fragrance. Although some supplement companies claim that raspberry ketones promote weight loss and increase lean body mass, there really isn’t enough scientific evidence that proves these claims to be true, at this point in time.

There are some studies involving rodents that have mixed reviews, but suggest that raspberry ketones may help to reduce food intake and thereby promote weight loss. A 2017 animal study out of Ohio State University found that raspberry ketone supplementation has limited benefit in fat loss beyond reducing food intake in mice fed a high-fat diet.

9. Taurine

Taurine is a type of amino acid that is found in the tissues throughout the body. It can also be produced in small amounts.

Taurine, or 2-aminoethanesulfonic acid, is a type of amino acid that is found in the body and is considered the most abundant amino acid in the heart, retina, skeletal muscle, brain and immune cells.

L-taurine is often added to energy drinks for those looking to take advantage of the potential taurine benefits. It’s also widely available in supplement form, and may be beneficial for people at risk for taurine deficiency, including those receiving parenteral nutrition or those with chronic heart, liver or kidney failure.

It is believed to be associated with a number of health benefits, such as increased fat-burning during exercise and improved heart health.

Risks and Side Effects

Thermogenic supplements can cause side effects, some severe, or longer-lasting health problems. Here are some of them.

1. Acute Liver Failure

As one of the largest organs in the body, the liver supports many essential metabolic functions, including transforming nutrients from the foods we eat into substances our bodies can use, processing harmful substances and breaking down fat for energy.

However, certain thermogenic supplements have been found to induce acute liver failure. It’s the loss of liver function that happens quickly, over days and weeks, instead of chronic liver failure, which happens slowly, over a longer period of time, such as in the case of an alcoholic.

2. Caffeine Overdose

In part because of its ubiquity, it’s simple to forget that caffeine is actually a drug. And because of the super high levels of caffeine often included in certain thermogenic supplements, it’s not uncommon for people to suffer a caffeine overdose. When this occurs, individuals can experience an increase in insomnia, nervousness, jitteriness and even vomiting.

It doesn’t take much for that to happen, either. Most supplements instruct users to take several pills a day. Combine that with a morning cup of coffee, some late afternoon tea and that’s a whole lot of caffeine in one person’s system.

Causing or increasing anxiety is also a major side effect of too much caffeine in the body. If you’re someone who suffers from stress or nervousness, caffeine can heighten those feeling and add anxiety to the mix. And if you are a naturally anxious person already, it’s likely you’ll experience increases in symptoms like fear, heart palpitations and tremors.

3. Chest Pain

Certain other active ingredients in particular thermogenic supplements can also cause adverse effects. Bitter orange, for example, is an herb made from the bitter orange tree. The extracts from bitter orange peel often appear in weight-loss supplements, but it’s now linked to such serious symptoms as chest pain, anxiety and even death.

4. Increases in Heart Rate and Blood Pressure

Another popular ingredient in weight-loss supplements is hoodia, a succulent African plant. Supposedly, the substance can trick your brain into thinking you’re full, but scant scientific evidence exists.

Instead, it’s known to cause significant increases in heart rate and blood pressure, plus can also impair liver function and cause headaches, dizziness and nausea.

5. Experiencing the “Unknown Cocktail” Effect

Many thermogenic supplements combine these active, potentially dangerous ingredients together. Dosage levels can be too high to begin with, but then combining these active ingredients together?

It also can be tough to isolate which ingredient a person will have a reaction to. Indeed, ingredients are often mixed up on labels or not even on the ingredients list; people could ingest something they’re allergic to unknowingly.