How Long Does Fat Burner Stay in Your System?

Weight loss is big business, especially in size-obsessed cultures. In the US alone, people spend about $2.1 billion per year on weight loss pills, including fat burners.

Yet, 45% of Americans are still overweight. And 67% of those are even trying to lose weight, according to the National Institutes of Health. If losing weight is really “quick and easy” as ads claim them to be, isn’t such statistic shockingly high?

Well, that’s because fat burners don’t drop off the weight like magic. They help people shed fat and boost metabolic rate, but they can’t outwork poor diet and lack of physical activity. However, if you want to strategize your weight loss routine, I suggest you learn about the supplement you are planning to take or are currently taking.

But first, let’s answer…

What Are Fat Burner Supplements?

Fat burners are dietary supplements that contain natural, artificial, or a combination of both compounds. Companies producing these products claim to help people get a more sculpted shape and lose pounds.

Do fat burners help lose weight?

Yes, but don’t expect any miracles. If you focus on the ingredients found in fat burners, they have been linked to weight loss, but further scientific studies are needed. Some ingredients often found in fat burners are proven effective when consumed naturally.

Be aware that the US Food and Drug Administration (FDA) doesn’t regulate them. So, always proceed with caution.

Read Next: How to Use Fat Burner for Weight Loss

How Do Fat Burners Work?

Fat burners are claimed to:

  • Enhance weight loss
  • Increase fat metabolism
  • Increase fat breakdown (lipolysis) during exercise
  • Cause long-term metabolic adaptations to enhanced fat metabolism
  • Or impair fat absorption

These dietary supplements contain different ingredients, such as caffeine, carnitine, green tea extracts, chromium, and conjugated linoleic acid (CLA). Each component works differently in the body but is involved in fat breakdown.

With exercise, fat burners pack a punch on fat cells.

So, How Long Does Fat Burner Stay in Your System?

It depends on the serving size, how often you consume, and what ingredients are used, among other things. But generally, fat burners stay in a healthy system from one hour to several hours. Caffeine, for instance, stays in your body for 1.5 to 9.5 hours.

Many fat burners work within a few minutes to 45 minutes after ingestion. The bioactive ingredients on the diet pills affect how long fat burners take to work in the body.

However, remember that a longer-lasting fat burner supplement does not always equate to being more effective.

8 Commonly Used Ingredients in Fat Burners and How Long They Stay in Your System

1. Caffeine

Caffeine is a common ingredient in fat burner supplements because it stimulates the nervous system and increases the resting metabolic rate, which consequently helps burn calories. 

Fat burners may contain more caffeine than your typical chocolate, tea, or coffee. 

Caffeine peaks in the blood about one hour later and stays at such a level for several hours. Half of the caffeine remains in your system six hours after caffeine is consumed. It takes up to 10 hours for caffeine to be entirely out of your bloodstream.

2. Carnitine

Carnitine is a chemical compound that plays a significant role in energy production and metabolism. Although it can be found in dairy and meat products and is made naturally by your kidney and liver, you can take advantage of its weight-loss benefits when included in a fat burner.

A review in the Obesity Reviews journal showed that adults who took carnitine significantly lost more weight than those in the control group. 

However, another study cast doubt on the efficacy of L-carnitine for weight loss. It showed that eight weeks of ingestion among overweight premenopausal women who do aerobic training did not significantly alter their total body mass (TMB) or fat mass (FM) compared to those who did not take L-carnitine.

In a pharmacokinetic study involving three healthy volunteers, a single administration of L-carnitine resulted in an increased level of carnitine serum at one, three, and six hours. When taken by mouth, L-carnitine supplementation is likely safe for 12 months and has a half-life of 60.3 ± 15 min.

Read Next: Best Fat Burner for Men Over 40

3. Green Tea Extracts

GTE is another common ingredient in fat burners because it helps lessen the fat you absorb from food and burn fat. 

Green tea contains caffeine, too, although about only half of what’s present in coffee. This natural fat burner has antioxidant catechin. The half-life of green tea is three to five hours and at peak level within 30-60 minutes. Half-life refers to the time it takes for the compound in your body to reduce by half.

4. Yohimbe

Yohimbe is a plant compound commonly found in fat burners because it can block the alpha-2 adrenergic receptors in fat cells. This ingredient can then lead to increased weight loss and fat loss. However, some controlled studies found mixed results.

Some studies claim that Yohimbe can cause headaches, increased blood pressure, agitation, anxiety, kidney failure, and heart problems.

5. Chromium

Chromium is another ingredient commonly found in fat-burning supplements that seems to lower glucose levels and enhance the effects of insulin.

A study published in the Nutrition Reviews showed that dietary intake of chromium in both humans and farm animals could decrease the percentage of body fat and increase lean body mass. These results may lead to weight loss.

Still, chromium in the fat burner pill is only a tiny part of the puzzle in controlling the effect of body composition. 

A separate pilot study in the Journal of Alternative and Complementary Medicine demonstrated that after two weeks of chromium picolinate supplementation, found no significant difference in the body mass index (BMI) of the chromium and the placebo group.

Most chromium stays in the system for eight hours. After that, it leaves the body through the urine.

6. Capsaicin

Capsaicin or cayenne pepper can turn up the body’s heat, boosting metabolism and increasing the number of calories burned. This same ingredient appears to impact fat oxidation by increasing the release of adrenalin.

Based on a study about the bioavailability of capsaicin, it takes 20 hours for the cayenne pepper to be metabolized in the human skin. So, why not consider adding natural fat burners, such as cayenne pepper, into your fitness routine? 

7. Soluble Fiber

Soluble (dissolves in water) fiber feeds your friendly gut bacteria, reduces the hunger hormones in the body, and promotes a feeling of fullness, which does not just help you lose fat but also helps you achieve a healthy weight.

Even a study shows that each 10-gram increase in soluble fiber decreases visceral fat accumulation by 3.7%. Visceral fat is stored in the abdominal cavity. Too much of it has been linked to disease—no wonder fiber is often found in fat burner pills.

How long fiber stays in the system varies from person to person. Generally, it takes around 24 – 61 hours for fiber to keep in the body, but other factors affect how long it takes to pass through the body. 

These factors include the activity level, general health, personal characteristics, psychological stress, and other foods a person eats. 

If the transit time of fiber is your concern, you can take steps to speed up things, such as working out for 30 minutes daily (digested material and food are moved through the body by muscle contractions), drinking more water, and eating less meat.

8. Conjugated Linoleic Acid (CLA)

Conjugated Linoleic Acid is a type of fat that help reduce body fat deposits. This ingredient helps oxidation and lipolysis (fat breakdown). It can also increase energy expenditure and decrease lipogenesis (fat production). 

However, many studies on CLA and its link to weight loss are conducted only on animals. So, it may not apply directly to humans. Another study found that CLA works for weight loss after 36 weeks, and its effects are most pronounced in the first six months.

How Do I Get The Most Out Of A Fat Burner?

  • Choose a thermogenic fat burner – These fat burners contain thermogenic ingredients that increase body temperature. As a result, this helps boost your metabolism and provides better workout performance.
  • Start training – If your goal is to lose weight, take time to do high-intensity workouts, strength training, or other forms of exercise that assist fat burners and accelerate the fat-burning process.
  • Avoid fat burner supplements that contain proprietary blends – Some ingredient lists on the back of a fat burner have a proprietary blend. However, this blend hides how much each ingredient is used or may contain fillers. 
  • Stay hydrated – Thermogenic fat burners are excellent aids to losing weight, but if the body temperature increases, it means lots of sweat is released. If a fat burner even contains caffeine, it’s more likely that you’ll go to the bathroom often. So, make sure to drink plenty of water for hydration support and optimal absorption of the nutrients in your body.
  • Sleep enough – Our body needs a good night’s sleep to function properly. Sleep helps repair muscle, regulate hormones, and restore damaged tissues. Just be aware, though, that most fat burners contain stimulants. Avoid taking these kinds of fat burners before bedtime. Read Next: Best Time to Take a Fat Burner

Final Words

There you go. You may know by now that how long a fat burner stays in your system is different for everyone, especially since these supplements differ in ingredients.

The good news is that plenty of high-quality fat burners out there to help you reach your weight loss goals. Just look at the ingredient list of a fat burner you’re planning to buy, and you’ll see that the ingredients individually provide a burn benefit, especially if you pair it with a consistent exercise plan and healthy eating. 

Most fat burners release slowly in the body from 12-24 hours but vary depending on how much you take in and how your body reacts. If you want to achieve lean body results without the side effect of an energy crash, opt for a stim-free fat burner.

However, fat-burning supplements do not guarantee rapid weight loss. You have to make lifestyle changes. The FDA does not regulate them. So, it is best to talk to your doctor, especially if you take medications.

If you like this article, you might want to read our other articles and reviews at

Nathan Lloyd, MSc

I’m a personal trainer, based in Boulder, Colorado.
I service clients physically in the Boulder area, mainly in the ONE Boulder Fitness Gym, but am also available for online consulting and coaching.

If you’re interested in my personal coaching programs, please contact me via the contact page.