6 Reasons That Will Make You AVOID Fat Burners For Weight Loss

Reviewed By Temple Stewart, RD, LDN, Registered Dietitian Nutritionist
Written by Swathi Handoo

Is weight loss on your mind?

Are you always looking for ways to avoid working out?

Are you thinking of taking fat burners?

Stop! Take a step back.

Do not pick up fat burners from that store shelf. You might be in for some major deception!

Fat burners are supplements that are supposed to help you lose weight rapidly. Many of us fall for those “instant results” claims. But the truth is they can do more harm than good.

There are scientifically-proven side effects of fat burners – some minor and some highly severe. Find out what they are here and then decide if it is safe to use fat burners or not.

Scroll down!

Fat Burners: What Are They?

The term ‘fat burner’ is used to describe nutrition supplements that help you burn fat. Fat burners claim to aid quick weight loss. They increase fat metabolism or energy expenditure rapidly.

They also alter fat absorption or trigger long-term changes to promote fat metabolism. When used during workout sessions, fat burners are supposed to increase fat oxidation (1).

These so-called natural products cause weight loss by either stimulating lipolysis (breakdown of accumulated fat) or inhibiting lipogenesis (synthesis/accumulation of fat) (2).

These supplements contain a variety of ingredients like caffeine, green tea, carnitine, conjugated linoleic acid, chromium, kelp, and fucoxanthin (1).

Let’s check out how a few of these additives work.

How Do Fat Burners (Claim To) Work? Are They Safe To Use?

Most of the ingredients in fat burners or diet pills speed up your metabolism. This stimulates the release of some neurotransmitters (like adrenaline and norepinephrine). These neurotransmitters trigger the release of glucose from the liver and the body’s fat reserve (adipose tissue) (3), (4).

By burning or mobilizing the stored fatty acids, these supplements aim to increase the production of energy (ATP). In other words, they use glucose and fat to produce energy. Therefore, you shed some pounds and get an energy boost as well!

Here’s a list of commonly found ingredients in fat burners (5):

IngredientProposed Mechanism of Action
African mango (Irvingia gabonensis)Inhibits adipogenesis and reduces leptin levels
Beta-glucansIncrease satiety and gastrointestinal transit time, and slow glucose absorption
Bitter orange (Citrus aurantium L.)Increases energy expenditure and lipolysis, acts as a mild appetite suppressant. Synephrine is the proposed active constituent.
Caffeine (as added caffeine or from guarana, kola nut, yerba maté, or other herbs)Stimulates central nervous system, increases thermogenesis and fat oxidation
CalciumIncreases lipolysis and fat accumulation, decreases fat absorption
Capsaicin and other capsaicinoidsIncrease energy expenditure and lipid oxidation, increase satiety, and reduce energy intake
CarnitineIncreases fatty acid oxidation
ChitosanBinds dietary fat in the digestive tract
ChromiumIncreases lean muscle mass; promotes fat loss; and reduces food intake, hunger levels, and fat cravings
Coleus forskohliiEnhances lipolysis and reduces appetite. Forskolin is the proposed active constituent.
Conjugated linoleic acidIncreases lipolysis, reduces lipogenesis, and promotes apoptosis in adipose tissue
FucoxanthinIncreases energy expenditure and fatty acid oxidation, suppresses adipocyte differentiation and lipid accumulation
Garcinia cambogia (hydroxycitric acid)Inhibits lipogenesis, suppresses food intake. Hydroxycitric acid is the proposed active constituent.
GlucomannanIncreases feelings of satiety and fullness, prolongs gastric emptying time
Green coffee bean extract (Coffea arabica, Coffea canephora, Coffea robusta)Inhibits fat accumulation, modulates glucose metabolism
Green tea (Camellia sinensis) and green tea extractIncreases energy expenditure and fat oxidation, reduces lipogenesis and fat absorption
Guar gumActs as bulking agent in gut, delays gastric emptying, increases feelings of satiety
Hoodia (Hoodia gordonii)Suppresses appetite, reduces food intake
ProbioticsAlter gut microbiota, affecting nutrient and energy extraction from food and altering energy expenditure
PyruvateIncreases lipolysis and energy expenditure
Raspberry ketoneAlters lipid metabolism
Vitamin DNone proposed; associations exist between low vitamin D status and obesity
White kidney bean (Phaseolus vulgaris)Interferes with breakdown and absorption of carbohydrates by acting as a “starch blocker”
Yohimbe (Pausinystalia yohimbe)Has hyperadrenergic effects. Yohimbine is the proposed active constituent.

The ingredients in fat burners improve your endurance, alertness, memory, feeling of vigor, and reduce fatigue. In a way, they enable you to train longer and harder. All of this to just burn more fat!

Logically and theoretically speaking, this is mind-blowing! But, research shows an entirely different picture.

The secreted neurotransmitters may not always have desired effects. They can increase your heart rate and blood pressure. A few ingredients can cause vasodilation (constricting blood vessels) and expanded airways (4).

Therefore, fat burners can be dangerous for your health. In fact, the scientific community goes to the extent of calling them all bogus!

Do you want to know how they affect your health? Jump to the next section.

What Are The Harmful Effects Caused by Fat Burners?

Fat burners are supposed to aid weight loss. Instead, they affect your liver, heart, brain, and appetite. Here’s how and why this happens.

1. Liver Damage

Despite several claims about the safety of herbal weight loss supplements, researchers have reported multiple episodes of hepatotoxicity. Certain fat burners contain an ingredient called usnic acid. This, along with green tea and guggul tree extracts, has been found to cause liver damage (6).

A healthy 28-year-old woman had acute liver failure within a month of taking 500 mg/day of pure usnic acid for two weeks. Kombucha tea is another herbal supplement that contains usnic acid. It has also been reported to be hepatotoxic (6).

Consuming fat burners with green tea extracts may cause jaundice and acute hepatitis.

Chromium polynicotinate, a common fat burner additive, is reported to cause acute liver injury.

Most such ingredients interact with plant extracts like Garcinia cambogia and heavy metal contaminants to cause liver damage (7).

2. Blood Pressure Fluctuation

Many of the ingredients found in fat burner pills or powders are legally banned in some countries as they can cause hypertension and fluctuations in blood pressure.

Compounds like phenylpropanolamine (PPA), fenfluramine, caffeine, and ephedrine also cause hypertension (8).

These compounds stimulate your central nervous system (CNS) to control appetite. However, they also adversely affect your blood pressure.

Herbal additives like bitter orange extract (Citrus aurantium) are said to interact with compounds like caffeine and synephrine. They increase your blood pressure or cause fluctuations by constricting blood vessels (1), (5).

3. Anxiety And Headache


High doses or chronic consumption of weight loss supplements can lead to anxiety. Supplements containing bitter orange extract, caffeine, and yohimbe may give you a headache along with anxiety (5).

Green coffee bean extract too can cause panic attacks. Moreover, fat burners that contain caffeine are too hard on your heart. If you have heart problems, it is recommended you stay away from fat burners and caffeinated supplements (9).

4. Heart Attack

Obesity is one of the main risk factors for heart attacks. Taking diet pills, fat burners, or weight loss medication might sound like an easy and quick way out. But, recent studies have proven the lethality of these supplements.

While burning fat, these supplements may affect your cardiovascular health. Fat burners may cause cardiac arrhythmia and even heart attacks.

A (in)famous banned weight loss drug is ephedra. In fact, any supplement containing ephedrine alkaloids are prohibited in the United States (5).

Aspirin is another additive in fat burners. It is added to ensure longer retention of the drug in the bloodstream by lowering the urinary excretion. When combined with caffeine or any over-the-counter blood thinner, aspirin can trigger a heart attack (10).

5. Nausea And Diarrhea


Many weight control drugs/pills limit your appetite by exerting an anorectic effect on your body. This may lead to nausea and diarrhea (5).

Fat burners stimulate your CNS to delay gastric emptying and induce a feeling of satiety. When you take fat burners that contain guar gum, carnitine, green tea extract, chromium, or chitosan, you may experience nausea and vomiting (5).

What’s worse is that most of them don’t even affect your body weight, let alone aid weight loss!

6. Insomnia

Green coffee bean extract and other caffeine-rich supplements are said to control your blood glucose levels.

The active ingredient in it, chlorogenic acid, along with caffeine, is supposed to slow down your body’s absorption of glucose. Indirectly, this is supposed to promote weight loss (11).

However, research has found this effect only in a few individuals. In most people, these active compounds cause insomnia and increased heart rate. Sleeplessness is again linked to obesity and weight gain (12).

In other words, you will neither lose weight nor have a good night’s sleep.

So, now you know that fat burners are just a bunch of lies!

Most of the literature available today tells you not to use these drugs/supplements. There is probably just a tiny fraction of people that benefit from them.

How do the rest of us lose weight then? What’s a safer way to lose weight? Read on to find out!

How To Prevent The Side Effects Of Fat Burners And Safely Lose Weight

Yes, it is true. Obesity is a growing menace around the world. Hence, it comes as no surprise that almost anything in the name of weight loss sells today. Every other person wants or needs to lose weight! And in an effort to do so, many of them fall for the concept of “quick weight loss.” Fat burners are a fad born out of this concept.

But, we have already told you about the repercussions of weight loss supplements. We have almost forgotten the idea of healthy weight loss!

Remember (13):

  • Healthy weight loss always takes time.
  • Both your body and your mind need to be controlled. Yoga, meditation, and mindful/ clean eating are some tools you can use along with other weight loss interventions to do.
  • Count your nutrients too – not just your calories.
  • Stick to the said limit. Do not exploit/overconsume these substances.
  • ‘Natural’ does NOT ALWAYS mean ‘safe.’
  • Talk to a nutritionist. Self-medication can be fatal.


  • If you are diagnosed with a cardiovascular disease, diabetes, or anorexia, stay away from these supplements. Consult your doctor for instructions to use if any.
  • The safety of fat burners in pregnant and nursing women has not been studied. It is better to avoid their usage.
  • Do not use fat burners or any such supplements without medical consent/guidance..


If you are taking fat burners, and if they have worked for you, great!

But, if you are experiencing any of the side effects discussed above, stop taking them immediately. Consult a healthcare provider about your problems to figure out if fat burners are the reason behind them.

More importantly, you need to stop believing in quick weight loss. Follow a healthy lifestyle, diet, and physical routine, and your weight will never be a problem!

Share your comments, experiences, and questions about fat burners in the comments section below, and we’ll get back to you.

Be smart and chuck that fat burner!


  1. Fat burners: nutrition supplements that increase fat metabolism.” Obesity Reviews, US National Library of Medicine.
  2. Risks associated with fat burners: A toxicological perspective.” Food and Chemical Toxicology, US National Library of Medicine.
  3. Facts About Fat Burners” Weight Loss, International Sports Sciences Association.
  4. Do “fat burners” really work?” Go Ask Alice!, Columbia University.
  5. Dietary Supplements for Weight Loss” Health Information, Office of Dietary Supplements, National Institutes of Health.
  6. Acute liver failure caused by ‘fat burners’ and dietary…” Canadian Journal of Gastroenterology, US National Library of Medicine.
  7. Hepatotoxicity Due to Hydroxycut: A Case Series” Liver, Original Contributions, The American Journal of Gastroenterology, The American College of Gastroenterology.
  8. Toxicity of Weight Loss Agents” Journal of Medical Toxicology, US National Library of Medicine.
  9. Green coffee caution” MSU Extension, Michigan State University.
  10. Diet Pills: Fat-Burning or Risk-Taking?” CU Sports Medicine, Information for Patients and Families, University of Colorado Hospital.
  11. Claim vs. Truth: Do Weight-Loss Supplements Really Work?” Get-U-Fit Blog, Warhawk Fitness & Aquatics, University of Wisconsin Whitewater.
  12. The link between sleep deprivation and weight gain” Evidence-based Living, Cornell University.
  13. Weight Control” National Center for Complementary and Integrative Health, National Institutes of Health.

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Swathi holds a Master’s degree in Biotechnology and has worked in places where actual science and research happen. Blending her love for writing with science, Swathi writes for Health and Wellness and simplifies complex topics for readers from all walks of life.And on the days she doesn’t write, she learns and performs Kathak, sings Carnatic music compositions, makes plans to travel, and obsesses over cleanliness.