Written by Garett Reid | NSCA, CSCS, CISSN, M.S.E.S.S
Fact checked by Andrew Lenau, ISSA CPT & Sports Nutritionist
FACT CHECKED
Men and women of all ages flock to fat burning supplements as a method to help torch fat, lose weight, and burn calories quickly.
Fat burners are also relatively cheap and readily available for purchase at stores everywhere, making them a quick go-to for weight loss.
But just because something is convenient to buy doesn't necessarily mean it's safe. And fat burners have definitely been given a bad rap over the years, even being labeled by some as dangerous.
So, what's the deal with fat burners? Are they safe to use or bad for your health?
This article is doing to dig into this topic, so you can make an informed decision on whether fat burners deserve a spot in your supplement line-up.
Table of Contents:
- What Is A Fat Burner?
- Are Fat Burners Safe?
- How Do Fat Burners Work?
- Does A Fat Burner Really Burn Fat?
- Common Fat Burner Ingredients
- Risk Factors of Fat Burners
- Who Should and Shouldn't Use Fat Burners?
- Final Takeaways
**For full transparency, this post may contain affiliate links where we could earn a commission on a purchase you make at no additional cost to you. We only recommend products that we have thoroughly researched and think you will find valuable.**
What Is A Fat Burner?
Thermogenic fat burners are a group of nutritional supplements designed to help increase your metabolic rate, in turn burning extra calories.
While generally taken in combination with exercise and a calorie-restricted diet, fat burners work independently of these. In other words, the premise behind fat burners is that simply by taking them, you will increase your calorie burn.
For more information on this, check out our article that explains what a fat burner is.
Are Fat Burners Safe To Take?
This question is complex as there are multiple variables to take into account.
The most important one to consider: Which fat burner are you talking about? You see, the term fat burners is an umbrella term for a type of nutritional supplement. As a result, fat burners contain a wide list of different ingredients, with each brand differing in what's included and the amount of it included.
Therefore, while one fat burner may be potentially harmful, another may be perfectly safe. Your best bet is to stick with ingredients like the ones highlighted in our article on the 8 Best Supplements For Fat Loss, as these are all natural vitamins, minerals, and herbs.
That said, when taking fat burners as a whole without the nuance, they’re more than likely safe if you take them as directed. We’ll explore this more shortly.
How Do Fat Burners Work?
Fat burners work by stimulating the central nervous system, which can lead to various reactions.
Some of the things fat burners claim to do include: increase fat metabolism or energy expenditure, impair fat absorption, decrease fat cells, increase fat oxidation during exercise, and cause long-term adaptations that promote fat metabolism¹.
The most common claim is that fat burners will increase your metabolism.
How Fat Burners Affect Your Metabolic Rate & Metabolic Systems
Before we go any further, it's important to differentiate between our metabolic rate and metabolic systems. Our metabolic rate refers to our total energy expenditure throughout the day. This total is comprised of several categories, all of which require calories.
- Basal Metabolic Rate (BMR): Your BMR refers to the number of calories your body burns for basic function. If you were to just lay down all day, your body would still burn calories to support respiration, brain function, processing, and your heartbeat. This is your BMR.
- Physical Activity: Physical activity can be divided into two parts: exercise and non-exercise activity thermogenesis (NEAT). Exercise is any type of unnecessary movement you do that is for the purpose of exercise or sport. This includes activities such as running, lifting weights, and cycling. NEAT is movements throughout the day that are necessary for living and not done with the intention of sport, which includes things like walking to the store or cooking food.
- Thermal Food Effect (TFE): TFE is similar to BMR, but it's the number of calories your body needs to digest food and absorb its nutrients. The reason it's separate from BMR is your TFE will change depending on the food you eat.
Of these 3 (technically 4) different categories, fat burners primarily work by increasing your BMR. It increases some of your physiological systems, requiring more energy expenditure.
Fat burners can also increase physical activity by providing you with more energy, causing you to move more and burn body fat. You can learn more about this in the article: What Happens If You Take Fat Burners Without Working Out?
Does A Fat Burner Really Burn Fat?
Terms such as "burning fat," "fat loss," and "fat burners" are usually major exaggerations. For example, even sitting down to read this article, you're actually burning fat for fuel, but would you describe reading articles as "fat burning?" And keep in mind that even when something does burn fat, if you eat too many calories, it won't translate into fat loss.
Further, just because your metabolism speeds up doesn't necessarily mean you're burning fat for fuel. Remember, the same principles that dictate your metabolic systems, mainly intensity, dictate if you use carbs, fat, or protein for fuel.
In other words, if your metabolism increases, your body will use either fat or carbs depending on your fed state and intensity of exercise. But despite all of this, if you eat more than you burn, fat loss won't lead to weight loss.
Most Popular Fat-Burning Ingredients
As fat burners work by increasing your thermogenic rate, the primary active ingredients in fat burners are going to stimulate your central nervous system, increasing multiple physiological systems.
As a result, stimulants can increase weight loss through:
- Increasing physical activity
- Decreasing appetite
- Increasing metabolic rate
Here's a look at some of the more common fat burner ingredients.
Caffeine:
One of the most common ingredients in fat burners, caffeine is a compound found in various plants, seeds, and fruits and has been used for years as a psychoactive stimulant. Upon consumption, it stimulates your nervous system, which in theory, can help you burn more calories, resulting in weight loss.
Interestingly, research shows that caffeine does indeed increase fat oxidation². In addition, caffeine is used as a supplement for weight loss and has also been proven to be an effective ergogenic aide for both physical and cognitive performance³.
In fact, many endurance athletes use caffeine pills to help boost their athletic performance.
Carnitine:
Naturally produced in your body, carnitine is also found in many meat and dairy products. We dig into this ingredient in our article: Is L Carnitine Good For Weight Loss?
Green tea extract:
Green tea is quickly becoming a very popular fat-burner ingredient due to its caffeine content. As a bonus, green tea extract tends to provide a smoother, less intense buzz, providing sufficient energy without the crash.
In addition to green tea containing caffeine, it's also full of antioxidants known as catechins. Catechins are compounds that have also been found to increase metabolism as well as the body's ability to burn fat.
In terms of weight loss, studies have shown green tea leads to positive weight loss results⁴.
Yohimbe:
Derived from the bark of the Pausinystalia yohimbe tree, yohimbe has been used as an aphrodisiac as well as for its fat-burning potential.
Yohimbe is believed to be beneficial for fat loss because it blocks the receptors that control adrenaline, allowing it to stay in your body longer to increase fat burning.
Other Fat Burning Ingredients:
Please note that this list of ingredients doesn't come close to listing all of the potential ones used in fat burners. We've only highlighted a few of the most common. When selecting a fat burner, it's important to research the ingredient list as this will help you determine if it's safe and a good match for you.
For additional information on more fat-burning ingredients, check out our articles on the best fat burners for men, fat burners for women, non-stimulant fat burners, and nighttime fat burners, as we dig into more ingredients in each post.
4 Risk Factors Of Fat Burners
Now that we have a better idea of what fat burners contain and how they work, let's examine potential risk factors you should be aware of.
1. Unlicensed And Unregulated Compounds:
Before we begin this section, we want to be clear that nutritional supplements are generally safe. The idea that the supplement industry is "unregulated" is not true. However, there have been instances in which some companies have slipped questionable ingredients into their products. And, there's always the potential that a company may include a new compound in their product that hasn't been tested yet.
For example, a few years ago, low concentrations (<100mcg/kg) of a compound called 2,4-dinitrophenol (DNP) were found to be present in 14 of 98 products tested⁴. DNP was actually used in the 1930s for obesity until it was found to cause severe toxicity, but it's still used for industrial purposes and included in some fat burners.
Adulterants, a term used to describe secretly lacing supplements with contaminants that shouldn't be included, have also been found to be an issue in some fat burners⁵. These contaminants are used to suppress appetite and are cause for concern.
If you are going to use a fat burner, always use a trusted brand with 3rd party testing. Further, stick to the basics with your fat burning ingredients, rather than trying "new" compounds.
2. Liver Toxicity:
One concern is that the consumption of fat burners may lead to liver toxicity. A 2018 case study looked at 5 such cases. The patients were found to be using green tea extract (Camellia sinensis), garcinia gummi-gutta, green coffee beans, and spirulina (blue-green algae)⁶
Their symptoms were severe and included the following:
- Liver transplant
- Acute liver failure
- Acute hepatitis
Unfortunately, this is not the only case study, as there has been an increase in these cases over the years⁷. This case study in particular found that supplements containing usnic acid from green tea extract could likely be the cause of the liver issues.
3. Various Side Effects:
We're sure that everyone has experienced the effects of taking too much caffeine too late in the day, which leads to staying up too late and not getting enough sleep.
This is because many fat-burning supplements are stimulants that increase your metabolism and can, well, stimulate you.
As a result, it's not uncommon for some people, particularly those new to stimulants, to experience unwanted side effects, including:
- Increased blood pressure
- Increased heart rate
- Insomnia
- Nervousness
- Sweating
These are generally transient but could be an issue for some people, such as those who already have high blood pressure. The easy fix is to be aware of your health and start slow. Never take a full dose of any fat burner. Start with half to see how you react, and then go from there.
And if you have a health condition, always speak to your doctor before you begin taking anything.
4. Dependency:
Apart from your physical health, if you're not careful, using fat burners can also affect your mental health.
Dependency can happen with any type of supplement or drug. And when you combine fat burners with any body image issues you may have, it can be very easy to become reliant on them.
Who Should and Shouldn't Use Fat Burners?
Let's start by answering who shouldn't be taking them. Anyone who isn't currently prioritizing healthy eating and a consistent workout routine should avoid fat burners.
Why?
Because it indicates two things: 1) You likely have weight you can lose simply by changing your eating habits and exercising more. 2) If you don't have healthy habits in place, then weight gain will likely come back as soon as you stop taking fat burners.
To lose weight, getting into a 300-500 caloric deficit is recommended. That's the equivalent of going for an hour's walk and not eating a banana. The average person should have no trouble getting to the appropriate calorie deficit through diet and exercise. If you're looking for some good diet options, consider counting macros, the vegan diet, or the 80 20 rule diet.
Now, if you have your diet and exercise in check, are relatively happy with your body composition, and are just looking for a little added weight loss boost, a fat burner supplement may be a good option.
Interestingly, the group we believe would benefit the most from fat burners is one you wouldn't necessarily expect: Advanced bodybuilders with low body fat. This may seem surprising, but hear us out.
For one, the top bodybuilders have already demonstrated that they have control over their diet and exercise. More importantly, this population is at the elite level and has gotten there by mastering everything in their power. This means they have their diet and diet timing in check, emphasize muscle recovery and sleep, have shown control with other supplements, and have been consistent for an extended period of time.
In other words, the best bodybuilders have basically done everything they can to improve their physique. And once you get to a certain level of lean muscle mass, improving is even harder as there's such little room to play with. In this scenario, taking an effective fat burner could give them the extra boost they need.
To be clear, you don't need to be an elite bodybuilder to take a fat burner. If you have also perfected your diet and workout routine, are looking to lose a few more pounds, and feel confident you can take fat burners correctly, it may be a good option for you as well.
Just don't try to use fat burners as a shortcut to mask poor eating habits, as it's highly unlikely it will yield any long-term results.
At SET FOR SET, we've tested and reviewed many fat burners and our top pick is PhenQ.
PhenQ is a natural weight management system that targets 5 key areas of metabolic health to help shed excess fat, crush cravings, and support natural energy...
Are Fat Burners Safe? The Final Verdict
Assuming you're using established, brand-name supplements with the proper dosage, fat burners are likely completely safe, especially if you don't use them as a daily part of your regimen for an extended period of time.
It is, however, very important to keep in mind that while they can help boost your weight loss efforts, in the big scheme of things, they likely won't play that large of a role, particularly for long-term weight loss. In addition, research has found that single-ingredient, natural fat burners, such as green tea, are also pretty effective.
To summarize, yes, fat burners are most likely safe if you have no underlying health conditions and use big-brand, 3rd party tested supplements at the correct dosing for short-term use only.
Fat Burner Wrap-Up
Even though studies show fat burners are effective, this probably isn't the first supplement you should focus on during your weight loss journey. As far as priorities go, first, emphasize your diet and exercise and take supplements such as creatine and protein powder to support these goals.
Once your training is in check and you are following a healthy diet, you can optimize your weight loss by trying a fat burner. And remember, stick with a company that has 3rd party testing and avoid messing with new compounds.
Interested in trying a fat burner? Check out the best fat burners for women and the best fat burning supplements for men! Or, for options that help with fat-burning sans the jitters, take a look at the best nighttime fat burners and non-stimulant fat burner supplements.
References:
- Jeukendrup, A. E., & Randell, R. (2011). Fat burners: nutrition supplements that increase fat metabolism. Obesity reviews : an official journal of the International Association for the Study of Obesity, 12(10), 841–851. https://doi.org/10.1111/j.1467-789X.2011.00908.x
- Collado-Mateo, D., Lavín-Pérez, A. M., Merellano-Navarro, E., & Coso, J. D. (2020). Effect of Acute Caffeine Intake on the Fat Oxidation Rate during Exercise: A Systematic Review and Meta-Analysis. Nutrients, 12(12), 3603. https://doi.org/10.3390/nu12123603
- Pickering, C., & Grgic, J. (2019). Caffeine and Exercise: What Next?. Sports medicine (Auckland, N.Z.), 49(7), 1007–1030. https://doi.org/10.1007/s40279-019-01101-0
- Diepvens, K., Kovacs, E. M., Vogels, N., & Westerterp-Plantenga, M. S. (2006). Metabolic effects of green tea and of phases of weight loss. Physiology & behavior, 87(1), 185–191. https://doi.org/10.1016/j.physbeh.2005.09.013
- Petróczi, A., Ocampo, J.A.V., Shah, I. et al. Russian roulette with unlicensed fat-burner drug 2,4-dinitrophenol (DNP): evidence from a multidisciplinary study of the internet, bodybuilding supplements and DNP users. Subst Abuse Treat Prev Policy 10, 39 (2015). https://doi.org/10.1186/s13011-015-0034-1
- Jakopin Ž. (2019). Risks associated with fat burners: A toxicological perspective. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 123, 205–224. https://doi.org/10.1016/j.fct.2018.10.051
- Gavrić, A., Ribnikar, M., Šmid, L., Luzar, B., & Štabuc, B. (2018). Fat burner-induced acute liver injury: Case series of four patients. Nutrition (Burbank, Los Angeles County, Calif.), 47, 110–114. https://doi.org/10.1016/j.nut.2017.10.002
- Yellapu, R. K., Mittal, V., Grewal, P., Fiel, M., & Schiano, T. (2011). Acute liver failure caused by 'fat burners' and dietary supplements: a case report and literature review. Canadian journal of gastroenterology = Journal canadien de gastroenterologie, 25(3), 157–160. https://doi.org/10.1155/2011/174978
Garett Reid
Author