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Can Fat Burners Cause Diarrhea? (According to Science)

Isaac Robertson
Published by Isaac Robertson
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: February 28, 2023
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As a fitness coach, I've noticed that people usually overuse fat burners and so-called diet pills when trying to lose weight.

This can cause diarrhea and other side effects, and the blame is almost exclusively put on weight loss supplements. I’m here to explain why this happens and how you can avoid it.

Quick Summary

  • fat burners can cause diarrhea and other side effects if not properly taken, or if your body is sensitive to a specific brand.
  • These supplements stimulate the central nervous system to increase your metabolism and also stimulate the brain to boost your metabolism.
  • Fat burners have proven effective in helping many people attain their weight loss goals.
  • Green tea, L-carnitine, CLA, Yohimbine,and Garcinia Cambogia, are the ingredients found in fat burners.

What Does a Fat Burner Do?

As explained in the Obesity Reviews journal, fat burners are

"nutrition supplements that are claimed to acutely increase fat metabolism or energy expenditure, impair fat absorption, increase weight loss, increase fat oxidation during exercise, or somehow cause long-term adaptations that promote fat metabolism [1]."

— A. E. Jeukendrup, Sports Nutritionist & Exercise Physiologist, & R. Randell, Associate Professor in Applied Health Research

However, fat burners have a wide range of functions, and depending on their ingredients, and they can affect you differently.

Most commonly, fat burners and diet pills are designed to enhance weight loss by stimulating hormonal reactions in your body, breaking down fat, and using it as an energy source.

Most fat burners are made with stimulants, and thermogenic that speed up your metabolism and help you burn more calories during exercise and while resting.

Do They Help You Lose Weight?

A measuring tape squeezing a person's stomach

Yes, fat burners can help you lose weight, as long as you have realistic expectations.

Fat burners won't melt away all your pounds in a month while you sit around binge eating junk food.

Fat burner pills are just a little boost for your metabolism, and even the best fat burners won’t fix a bad diet.

For the fat burner to work, you have to stick to a healthy diet and exercise regimen.

A safe fat-loss pace is about 1–3 pounds a week for healthy people. No matter if you're using a fat burner or not, dropping weight too fast can cause some serious side effects and cost you a lean muscle mass.

You should set weekly or monthly weight loss goals and stay on track with your fat loss with a high-quality fat burner.

Are Fat Burners Safe?

Yes, fat burners are safe and won’t affect your health as long as you follow the instructions and use them accordingly.

Using too many fat-burning supplements or any other dietary supplements won't result in a greater weight loss, but it may result in severe side effects and put your health at risk.

What’s in Fat Burners? Most Common Ingredients

A hand holding supplements and a question mark

There are two types of fat burners — stimulant-free and those that contain stimulants.

  • Caffeinated fat burners are an excellent choice for people who struggle to find energy for a lengthy cardio session or a hard workout. Research has proven that caffeine is a potent appetite suppressant that slows down your body’s glucose absorption, which means that fat burners containing this ingredient are great for people who need to curb their cravings. Moreover, athletes love using caffeine to burn fat, but it also improves their endurance, meaning they could go for more extended periods in the gym and sports [2]. But, no matter how effective it is, it works best when combined with other ingredients. Just be careful if you use caffeine-only fat burners, as you can experience rapid heart rate, elevated blood pressure, and diarrhea.
  • Green tea and green tea extract are very efficient in activating your body’s thermogenic fat-burning activity. Taking a supplement with a combination of green tea and caffeine can burn fat more efficiently.
  • L-carnitine is a stimulant-free amino acid athletes use to help the body convert stored fat into energy, thus leaving you with leaner and more defined muscles.
  • CLA, or conjugated linoleic acid, is a naturally occurring fatty acid, similar to Omega-6 fatty acids. Even though fat itself CLA helps your body burn fat while retaining your muscles during weight loss.
  • Yohimbine is an excellent fat-burning stimulant. However, it's known to cause high blood pressure (which can lead to a heart attack if not treated), cause anxiety, and jitteriness, so get medical advice, diagnosis, or a recommendation from your doctor if you believe it may cause you to become anxious or jittery.
  • Garcinia cambogia is a very potent caffeine-free acid fruit extract that can help you control your appetite.

Can Fat Burners Cause Diarrhea?

A woman holding a tissue roll and her stomach

Yes, fat burners can cause diarrhea. For that matter, any diet pill or drug can cause diarrhea and other serious side effects if not taken correctly.

But don't give up on these supplements yet! Whether or not you'll experience diarrhea or any other side effects depends on a couple of factors.

Fat burners function in two ways. One is to stimulate your central nervous system to increase your metabolism, while the other is to stimulate your brain to boost your metabolism.

Your body may be too sensitive to a specific fat burner blend, which may result in diarrhea. This is why you shouldn't take any diet pill or fat burner before you get advice, diagnosis, or treatment from your doctor.

If they decide it's safe for you to use a fat burner medication, you should use only FDA-approved ones. Stay away from fat burners that have ephedra. This is a harmful ingredient banned by the FDA that causes extreme side effects.

So, why do fat burners cause diarrhea? The majority of fat burners contain stimulants, which stimulate your intestinal tract and the rate at which your body digests food.

As I already mentioned, most fat burners have caffeine, and large amounts of caffeine can cause diarrhea. Besides diarrhea, you may also experience nausea, lightheadedness, and dizziness.

Also Read: Can Fat Burners Cause Fertility?

Warning and Considerations

A woman showing index finger warning with a serious face

With each bowel movement, you lose many fluids, so having diarrhea for long periods can be dangerous to your health.

If you lose too much water, you may experience dehydration and an imbalance in electrolytes. This can furthermore lead to stomach pain, rectal bleeding, or fever.

Contact your physician if you have diarrhea that lasts for more than three days, as constant diarrhea can also be a sign of liver damage.

Conclusion On Fat Burners Causing Diarrhea

Taking a fat burner or a weight loss pill is an excellent way to give your metabolism a quick boost, but it can be dangerous if you go overboard. Stop taking the supplement and contact your physician if they affect your health.

The safest way to lose weight is to go slowly, eat good food, and use supplements and drugs checked by the FDA. Your safety should come first.


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