How Do Thermogenic Fat Burners Work?

Thermogenic fat burners purportedly work by increasing your metabolism.
Image Credit: AndreaObzerova/iStock/GettyImages

Want to burn more calories without spending hours in the gym? In this case, you might consider using a thermogenic fat burner to boost your metabolism. Unfortunately, these supplements carry serious side effects and may not be worth the risk, however.


If you do decide to take fat burners, first make sure your diet is in check. No diet pill can offset the damage caused by poor nutrition.

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Thermogenic fat burners purportedly work by increasing your metabolism. Some claim to suppress appetite, stimulate fat breakdown and inhibit fat storage.

Unfortunately, these dietary supplements lack scientific evidence and carry serious side effects. They may cause modest weight loss, but the risks often outweigh the benefits.

The Skinny on Diet Pills

Each year, Americans spend billions on weight loss supplements. Yet, obesity rates are on the rise. More than two in three adults and one in six children and teens have obesity, according to the National Health and Nutrition Examination Survey.

Diet pills are widely available in most stores, from supermarkets to pharmacies. Consumers can opt for thermogenic fat burners, carb blockers, prescription weight loss medications and everything in between. These products guarantee fast results but say nothing about diet or exercise. The question is: do they really work?

Dietary supplements, including over-the-counter weight loss pills, are regulated differently than prescription drugs by the Food and Drug Administration (FDA). In fact, you don't really know what's inside the bottle. Some products may contain too little or too much of the active ingredient. Others carry side effects, from heart palpitations and breathing problems to digestive discomfort.


For example, a June 2017 review published in the Malaysian Journal of Medical Sciences describes the side effects of several diet pills available in the U.S. and overseas.

Ephedra, a popular ingredient in weight loss supplements, caused death in several young, healthy adults. This natural compound affects the nervous and cardiovascular systems, promotes the formation of kidney stones and increases the risk of cardiac events.


Garcinia cambogia, chromium picolinate, Aristolochic acid and other ingredients in diet pills have all been linked to adverse health outcomes, including liver inflammation, kidney failure and hepatotoxicity. Individuals with diabetes, heart disease and other pre-existing conditions are more likely to experience these side effects.

About 15 percent of Americans have used diet pills at some point, as reported by the National Institutes of Health (NIH). Unfortunately, little is known about their safety and effectiveness. These products can interfere with certain medications or worsen existing conditions. Additionally, most formulas lack scientific evidence.



Prescription diet pills appear to be more effective, but there is still a risk of side effects. When combined with diet and exercise, these products may reduce body weight by 3 to 9 percent, according to the U.S. Department of Health and Human Services.

Again, it's your diet and exercise habits that matter most. Weight loss medications and supplements alone are unlikely to help you reach a healthy weight.


Read more:The 7 Principles of Fat Loss

What’s a Thermogenic Fat Burner?

Several types of diet pills exist and each has a different mechanism of action. Thermogenic fat burners, for example, work by increasing your metabolic rate, which in turn, leads to weight loss. As their name suggests, these supplements are designed to burn fat. The term "thermogenic" comes from thermogenesis, or heat production.


Certain foods increase energy expenditure, which is known as diet-induced thermogenesis, according to a September 2018 research paper featured in the Journal of Endocrinology. Depending on their composition, they can boost your metabolism by 10 to 15 percent over several hours.

Read more:The Metabolism Whisperer Shares Secrets for Burning More Calories


Likewise, thermogenic fat burners contain food ingredients, spices or herbs that raise your metabolic rate. Caffeine, green tea extract, garcinia cambogia and bitter orange are just a few examples.

To put it simply, a thermogenic burner will cause your body to burn more calories at rest and during exercise. While it sounds good in theory, weight loss is a lot more complex than that. These supplements are not just controversial but dangerous.


A recent review published in Food and Chemical Toxicology in January 2019 assessed the safety and efficacy of fat burners. As the researchers note, these products are intended to facilitate weight loss either by stimulating fat breakdown or inhibiting the formation of new fat cells. Depending on the brand, they may contain one or more active ingredients that claim to increase metabolism and fat oxidation.

Caffeine, for example, may inhibit lipogenesis, or the formation of fat. Green tea extract may reduce glucose absorption and suppress appetite. L-carnitine may increase fat oxidation and help your muscles use fat for energy. Garcinia cambogia extract, forskolin, capsaicin, raspberry ketones and other ingredients in fat burners have similar effects, according to the above review.

The problem is that these ingredients may not be safe and can interact with each other, as the scientists point out. Additionally, only a few have been studied in terms of tolerability. Even fewer have been proven effective for weight loss.

Do Thermogenic Fat Burners Work?

Most studies conducted on fat burners are small, so the results may not be conclusive. Some were sponsored by supplement manufacturers, making it difficult to assess their validity.

For example, a small study in the Journal of Sports Science & Medicine in December 2017 evaluated the effects of a thermogenic supplement on body composition, metabolism, hormone levels and muscular performance in 20 resistance-trained male subjects. The participants used a fat burner containing green tea, l-carnitine, panax ginseng, chromium picolinate and other ingredients that promote weight loss.

By the end of the study, the participants gained lower body strength and experienced a reduction in the levels of the stress hormone cortisol. However, the supplements produced no improvements in terms of body composition (muscle-to-fat ratio) or hormone concentrations.


Other studies, though, suggest that certain ingredients in thermogenic formulas may facilitate weight loss. Take caffeine, for example.

According to a November 2016 review published in the ‌Journal of Basic and Clinical Physiology and Pharmacology‌, this natural compound may raise energy expenditure and decrease energy intake while increasing fat oxidation. Researchers state that caffeine may suppress appetite and counteract the metabolic slowdown that tends to occur during dieting.

Another research paper, which was featured in the Cochrane Database of Systematic Reviews in December 2012, found that green tea supplements may cause a small reduction in body weight.

Capsaicin, a popular ingredient in thermogenic fat burners, may increase metabolism and improve appetite control during periods of energy restriction. More research is needed to determine its safety in the long run.

However, these compounds have been studied individually. A thermogenic fat burner may or may not contain enough of the active ingredient to produce results.

Additionally, it may cause adverse reactions ranging from mild digestive discomfort to liver injury. Some of these products contain potentially harmful ingredients that have been banned by the FDA, which may increase the risk of side effects.


Use thermogenic fat burners with caution. Check the labels and research each ingredient. If you’re sensitive to stimulants, avoid any products containing caffeine, green tea extract, ephedrine and other similar compounds.

Discuss your options with a medical professional who may recommend a diet plan and supplements that meet your individual needs.




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