How Do Fat Burners Work? (And, Are They Actually Effective?)

How do fat burners work (and, are they actually effective)

We’re constantly bombarded with diet products telling us that losing weight is “quick and easy”. Yet the National Institutes of Health reports that 45% of Americans are overweight and 67% of those are trying to lose weight.

If losing weight really was as easy as taking a pill or supplement, would this statistic still be so shockingly high?

This doesn’t stop a whopping 15% of U.S. adults from using a weight-loss supplement at some point in their lives. Collectively spending an average of $2.1 billion a year on them!

As a registered dietitian with years of experience helping people with their weight, I had to seek out the science behind the question: how do fat burners work?.

Fat burners work by speeding up metabolism, burning fat, and suppressing appetite. Yet the majority of these products contain ingredients that are not well researched. To burn fat, you should focus on a healthy eating and exercise strategy first, then consider adding natural fat burners to your routine.

Let’s get revved up on the research behind how fat burners work and what ways they may be effective in helping us melt fat and whither away excess weight.

What Are Fat Burners?

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Fat burners are supplements that claim to help increase metabolism, burn fat, and promote weight loss. Some are natural but many are processed and contain a long list of unhealthy ingredients.

They can be classified according to their intended “fat burning” action in the human body.

Related Article: Eat More to Lose Weight? Yes, It’s a Successful Strategy


Science Direct defines thermogenesis as the dissipation of energy through the production of heat. It’s literally defined as heat production in our body.

Thermogenesis is part of the normal metabolic process. When supplements market their products as increasing thermogenesis, this means they are designed with the intention to boost metabolism and therefore increase fat utilization and burn.

Related Article: How To Eat Less: 12 Easy To Follow Tips


Lipolysis is defined as breaking down lipids, otherwise known as fat. This is a process that happens in our bodies through enzymes and water.

According to the Biology Dictionary, lipolysis occurs in our adipose tissue. This is the fat that lines and protects our body and organs.

Our body naturally stores excess energy we eat as fat. This stored source of energy is ready and available when glucose stores run low.

Glucose is the preferred source of fuel for the body and brain but when we burn through it via lack of nutrition or intense exercise, our bodies facilitate movement of these stored fats to use as energy.

Related Article: 8 Healthy Lunch Ideas For Weight Loss (Low-Calorie Lunches)


Appetite is one of the main reasons why we eat. It’s the signal our body sends to our brain when it’s time to eat. It can be due to hunger but can also be stimulated without hunger, such as with cravings or when we see something that makes us want to eat.

Appetite suppressant supplements claim to decrease our appetite, therefore decreasing the urge to eat. They work in different ways including blocking the absorption of macronutrients which contain calories. They also work by making our stomach feel full, such as in the case of fiber (more details to come).

Appetite suppressants can also impact hunger hormones such as ghrelin. Ghrelin is known as the “hunger hormone” because it increases our urge to eat. Leptin is another hunger hormone which helps us feel satisfied.

Learn more about hunger hormones in this Today’s Dietitian article: Appetite Hormones.

Dangers of Fat Burners

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According to the  National Institutes of Health, the dangers of some of these weight loss products is that manufacturers market them with various claims that have not been well researched or clinically validated. Data is limited and it comes from animal or lab studies instead of validated human clinical trials.

The U.S. Food and Drug Administration (FDA) regulates dietary supplements, however unlike drugs, supplements do not require review before they’re sent to the market. This means that supplement manufacturers are responsible for determining if the products are safe. The claims on the labels are not always truthful and can be misleading.

These products typically contain a long list of ingredients with some reported as more than 90! The U.S. Government Accountability Office concluded that there’s little known about whether these supplements are effective but some have been associated with physical harm to the body.

Some of the ingredients can interact with certain medications and worsen disease related symptoms including high blood pressure or blood sugar issues. Particularly if you have a medical condition or take medication, please consult your healthcare provider.

For most all of the supplements we’ll be discussing, additional research is needed to fully understand the safety of and how well they work.

Related Article: What To Eat After Fasted Cardio? (5 Things To Know)

Common Fat Burners and How They Work


Ephedra comes from a shrub plant. It’s been used for centuries in China for colds, fever, flu, headaches, and nasal and lung issues.

As reported by the National Center for Complementary and Integrative Health, the FDA banned the sale of supplements containing ephedra compounds in 2004. At the time it was marketed for weight loss, improved athletic performance, and increased energy.

The FDA banned it because there was little evidence of ephedra’s effectiveness, except for short-term weight loss. But the very dangerous increased risk for heart issues and stroke cancelled out any observed benefits.

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Medlineplus explains that Orlistat is typically used with a prescribed low-calorie and low-fat diet and exercise program with the goal of helping people lose weight. It’s obtained by speaking with your doctor and getting guidance along with a prescription.

Orlistat is a lipase inhibitor, so it prevents some of the fat coming foods from being absorbed in the intestines. The fat that’s not absorbed gets excreted in stool. As a result, there can be side effects such as stomach upset, difficulty controlling bowel movements, and unpleasant stains on underwear.



Caffeine naturally comes from foods and drinks such as coffee, tea, and chocolate. It’s artificially added to energy drinks, soda, and also comes in the form of supplements. Caffeine is a known fat burner because it helps mobilize fat from tissue and can slightly increase metabolic rate because it’s a stimulant.

However, it’s important to recognize that releasing fatty acids doesn’t promote weight loss, unless you burn more calories than you consume.

A systematic review, found that caffeine may promote weight, BMI, and body fat reduction. One study showed that caffeine increased fat burn about three times more in lean people than obese.

Like any drug, the body and brain can develop tolerance to caffeine. So overtime, it will stop working in terms of energy boost and fat burn. Another thing to consider about caffeine is that too much, or having it too late in the day, can impact sleep — a key aspect of weight management and overall health.

What you add to your morning cup could cancel out the calorie burn. Check out: 7 Best Coffee Creamers For Weight Loss (Plus, 3 To Avoid).


Green tea contains caffeine but about half of what’s in coffee. Green tea also has an antioxidant called catechin. More specifically, epigallocatechin (EGCG) has been shown to boost metabolism.

Basically EGCG works by inhibiting the enzyme that breaks down norepinephrine (a fight-or-flight hormone). When norepinephrine increases there’s more potential to break down more fat.

A study review found that participants who were in the green tea group lost an average of 0.2-3.5 kilograms more than people in a control group. However in most of the studies, the weight loss was not statistically significant and the evidence doesn’t apply to brewed green tea, but rather green tea extracts.

Other studies found that green tea-caffeine mixtures improved weight maintenance through thermogenesis, fat oxidation, and sparing muscle.

Related Article: Should Strength Athletes Use The Keto Diet?


L-carnitine is an amino acid (protein building block) such as creatine. It’s naturally found in animal foods such as meat, fish, and eggs. People following a vegan diet have difficulty getting and producing enough of it. The body can naturally manufacture some of it with other amino acids including lysine and methionine, as long as there’s adequate vitamin C.

L-carnitine is thought to mobilize fatty acids into cells in order to be used as energy. So logically, it makes sense that it would help with fat burn. Studies are not showing this result though.

In one study in which women exercised, there was no difference in weight loss between those who took L-carnitine and those who didn’t.

In a review of nine studies, results showed that subjects who took carnitine lost significantly more weight when compared to the control group.

Due to conflicting results, it’s uncertain to say if L-carnitine will help with weight loss or not.

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Conjugated linoleic acid (CLA) is a fatty acid (building block of dietary fat). It’s naturally found in food such as dairy products and beef. It’s manufactured in supplement forms and claimed to reduce fat while increasing muscle and energy.

The American Journal of Clinical Nutrition found that a 3.2 g per day dose of CLA resulted in modest loss of body fat in humans. They also reported that there are no severe adverse effects, however it’s been shown to slightly increase markers of inflammatory disease and insulin resistance, which can be related to diabetes and weight gain.

Few CLA related studies have evaluated the use of CLA alone or in combination with physical exercise and changes in body composition. Therefore clinical evidence appears to be insufficient.

Related Article: Do Waist Trimmers Really Work? We Examine The Science


Yohimbine is a supplement made from the bark of an evergreen tree. It has been used in West African medicine to help improve sexual performance.

One study conducted on professional soccer players, found that when combined with resistance training, yohimbine did not significantly alter body mass, muscle mass, or performance. But it did appear to help promote fat loss.

In a small study of subjects on a very low calorie diet, the participants who took yohimbine did not show any increase in lipolysis (fat break down).

Due to the mixed results, more research is needed before it can be recommended as a weight loss supplement.


Medium-chain triglycerides (MCTs) oil usually comes from coconut oil but can also be found in palm oil and some dairy. It’s an oil that contains medium-length fat chains. Since they are shorter in length they are easier for your body to digest and use.

Since your body can use it as a direct fuel source, meaning it won’t necessarily be stored as fat. But studies show that this may only result in temporary benefits.

MCTs can be converted into ketones which are created when following a very-low carb diet. They’ve gained recent popularity due to the keto diet because they can help your body stay in a ketogenic state.

One systematic review and meta-analysis study found that replacing long-chain triglycerides (LCTs) with medium-chain triglycerides (MCTs) could possibly induce modest reductions in body weight and composition without negatively impacting cholesterol levels. But more research is required before confirming the efficacy and appropriate dose.


Garcinia cambogia comes from the rind of a tropical fruit. The rind contains hydroxycitric acid (HCA) which can block an enzyme that the body uses to make fat.

In a review by the Journal of Obesity, participants lost about 2 pounds more than people who didn’t take it. Researchers couldn’t conclude the loss was due to garcinia since it could have been due to the diet and exercise that participants were doing.

There are also many studies such as this one conducted on 135 subjects, which showed no significant difference in estimated percentage of body fat mass loss between groups who took it and not.

Garcinia cambogia is thought to block the body’s ability to make fat and decrease appetite. However research does not appear to be conclusive.


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Most people get enough protein from a well balanced diet. With frequent exercise and training, the body requires a bit more protein, at around 1.4-2 gram per kg, which can still be obtained through the diet.

Higher protein diets have been shown to help reduce appetite, burn fat, and increase satisfaction when compared to higher carb foods. Higher protein can also help balance blood sugar which stabilizes energy and limits cravings.

However, beware when choosing protein powders as a protein source. As Harvard reports, protein powder is a dietary supplement that’s not regulated by the FDA. We also don’t know the long-term effects since there is limited data on them.

Learn more: 30 Natural Food Sources of Creatine (+ How Much To Eat)


Fiber is the part of plant foods that can’t be digested by the human body, but it helps encourage healthy gut bacteria and health. It’s categorized by insoluble and soluble. Insoluble does not mix with water and can help things move through the gut.

Soluble fiber mixes with water and creates a thick gel like substance. Both are helpful for weight loss because they can promote fullness but soluble fiber slows how fast the stomach digests foods. Some studies found that eating soluble fiber reduces hunger hormones in the body such as ghrelin.

According to the American Society for Nutrition, fiber has been shown to promote a healthy microbiome, which can be a key to reaching a healthy weight.

Studies have shown that fiber can help with weight loss. This study found that for each 10 gram increase in soluble fiber, visceral fat accumulation was decreased by 3.7%. Visceral fat is stored within the abdominal cavity and is around a number of important internal organs. Too much visceral fat has been linked to disease.

Related Article: How To Lose 5lbs In A Month (The Healthy Way)

Final Thoughts

Fat burners are thought to help speed up metabolism, utilize fat, and decrease hunger. Yet many of the manufactured fat burning products have ingredients that could be harmful to humans. In addition, the research is very limited, making it difficult to state an honest health claim.

It’s best to aim for the more natural versions, such as caffeine found in coffee, versus a supplement with lots of unrecognizable and potentially unsafe ingredients.

Since these supplements have a slight burn benefit (if any) the key is to focus on an overall healthy eating and consistent exercise plan.

Fitbod can help you get stronger and reach your weight goals with a fitness plan that’s personalized to you.

About The Author

Lisa Booth

Lisa Booth

Lisa is a registered dietitian nutritionist (RDN) with over 15 years of experience in nutrition, fitness, and mental health coaching and education. She studied Foods and Nutrition at San Diego State University and earned a Master of Science in Holistic Nutrition at Hawthorn University.

Having certifications and experience in group exercise, intuitive eating, coaching and psychotherapy, and digestive wellness, she’s enthusiastic about the relationship between the body and mind.

She’s dedicated to helping people understand how to implement healthy habit change, while gaining a deeper understanding of what makes them feel their personal best.