Are Thermogenic Fat Burner Supplements Safe?

  • Medical Reviewer: Mahammad Juber, MD
Medically Reviewed on 10/13/2022

What does thermogenic mean?

A number of substances are thermogenic fat burners and they can increase your resting metabolic rate (RMR). Overall, individual thermogenic substances like caffeine and green tea are safe for most people.
A number of substances are thermogenic fat burners and they can increase your resting metabolic rate (RMR). Overall, individual thermogenic substances like caffeine and green tea are safe for most people.

As a mindful consumer, you’re likely suspicious of anything marketed as a quick, easy way to lose weight — but if you’re struggling to drop some pounds, it may not be easy to resist the siren song of speedy results. So, if you have heard that thermogenic fat burner supplements are the best path to accelerated weight loss with minimal effort, you’re probably asking yourself two questions: First, do they work? Second, are they safe?

The word “thermogenic” stems from the term “thermogenesis” and describes a tendency to produce heat. Thermogenesis is a biological process by which the body generates heat in order to maintain body temperature, which goes hand in hand with metabolism. Your metabolic rate is the rate at which your body burns calories and expends energy. Your metabolic rate is mainly established by genetics, but some thermogenic ingredients can slightly increase it.

Non Exercise thermogenesis describes the cumulative energy expended during normal daily activities, excluding exercise, and this type of thermogenesis can play a serious role when managing obesity.

Generally, thermogenesis happens when the body reacts to one of two things:

  • Colder temperatures (known as thermoregulatory thermogenesis)
  • Digestion (known as diet-induced thermogenesis)

Digesting food expends energy. When diet-induced thermogenesis occurs, your body is attempting to restore its energy balance by converting energy to heat.

What are thermogenic fat burner supplements?

Since food intake triggers thermogenesis, thermogenic fat supplements can increase your resting metabolic rate (RMR) and theoretically promote fat loss. However, the impact on RMR depends on the active ingredient or combination of ingredients in the thermogenic supplement.

A number of substances are considered thermogenic fat burners, and some of them may already be part of your diet:


The chemical stimulant caffeine is found in coffee beans, cacao, and tea leaves. Caffeine has been found to stimulate thermogenic activity, perhaps thanks to its tendency to promote physical activity and burn more calories during that physical activity. Caffeine can also suppress your appetite, therefore decreasing your risk of weight gain.

One study found that, on average, doubling caffeine intake resulted in a 22% increase in the rate of weight loss, 17% increase in the rate of shifting body mass index (BMI), and a 28% increase in the rate of reducing fat mass.

Due to the proven benefits of caffeine, it’s a common ingredient in many thermogenic fat burner supplements.

Green tea.

Green tea contains a low dose of caffeine, but that’s not the only reason it’s considered thermogenic.

Green tea has been found to promote fat oxidation and increase energy expenditure. This is due to its high amounts of polyphenols, which can reduce fat cells and inhibit their production. Polyphenols also have protein-binding properties that can encourage fat digestion.

Despite the health benefits of green tea, though, research results are mixed when it comes to green tea’s impact on weight. Most studies find that green tea makes minor contributions to weight loss at best.

Drinking green tea can raise your metabolic rate, but it won’t magically lower the number on your scale.


Yohimbine is the active ingredient in yohimbe, which is obtained from the tree bark of the African yohimbe evergreen tree.

While it’s a featured ingredient in some thermogenic supplements, yohimbine has not been studied extensively, and its purported health benefits are mostly unproven.


Your body naturally produces  carnitine, a compound that converts fat into energy.

A common form of carnitine is l-carnitine. One study found that when adults consumed 2000 milligrams of l-carnitine per day, their body weight decreased by an average of 2.7 pounds.

Yerba mate.

Yerba mate comes from the mate plant and contains caffeine and other chemicals that may contribute to weight loss. One clinical trial found that consuming yerba mate for 12 weeks led to a statistically significant decrease in waist-to-hip ratio, percentage of body fat, and body fat mass.


Capsaicin is what gives chili peppers their spicy kick, and it has many health benefits — including the potential to aid weight loss.

Capsaicin has been shown to prolong your sense of fullness following a meal, decrease weight gain, and increase energy expenditure when combined with exercise.

Eating chili peppers or thermogenic supplements including capsaicin may promote your metabolic health.

Thermogenic supplement side effects

Some ingredients commonly found in thermogenic fat burner supplements may be dangerous in high doses.

Thermogenic supplements containing caffeine may cause negative side effects due to caffeine’s impact on blood pressure and heart rate. Too much caffeine (generally defined as more than 300 milligrams per day) can also contribute to insomnia, stomach pain, nausea, restlessness, and an irregular heartbeat.

The high amounts of green tea extract found in some supplements can also be toxic and cause serious liver damage.

The approved daily dose of yohimbine is 30 milligrams. Therefore, any supplement containing a higher amount of yohimbine may not be safe and can even cause heart failure or death. One man taking 50 milligrams of yohimbine per day reported a number of negative side effects like headaches, high blood pressure, cold sweats, elevated heart rate, and tremors.

Although it’s generally considered safe, yerba mate can have similarly adverse effects on the body when taken in large amounts for a long period of time, increasing your risk of kidney, bladder, and mouth cancers (among others).

Do thermogenic supplements work?

While certain thermogenic ingredients have been demonstrated to promote weight loss, there is a lack of scientific research surrounding the overall level of effectiveness of thermogenic supplements when it comes to burning fat, reducing waistlines, or lowering BMI.

Still, over time, regularly taking thermogenic supplements may increase the amount of energy you expend on a daily basis and therefore aid in weight loss.

Are thermogenic fat burner supplements safe?

Overall, individual thermogenic substances like caffeine and green tea are safe for most people. Issues are more likely to arise when you’re considering thermogenic supplements containing many ingredients, high dosage levels, and questionable substances.

One study determined that a multi-ingredient thermogenic supplement was safe to consume for up to 6 weeks and that its participants saw a 16% reduction in the stress hormone cortisol. Even so, while most thermogenic fat burner supplements are not dangerous, it would be wise to carefully evaluate the ingredient list of each supplement or consult your doctor before adding it to your routine. 

When in doubt, remember that the safest and most effective fat-burning methods are exercise and a balanced diet — not supplements.


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Medically Reviewed on 10/13/2022

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Journal of Sports Science & Medicine: "Influence of A Thermogenic Dietary Supplement on Safety Markers, Body Composition, Energy Expenditure, Muscular Performance and Hormone Concentrations: A Randomized, Placebo-Controlled, Double-Blind Trial."

Minnesota Medicine: "Role of nonexercise activity thermogenesis (NEAT) in obesity."