Evidence Based Research
Our editorial team is made up of expert registered dietitians with extensive, real-world clinical experience who are highly trained in evaluating clinical research.
Read Our Editorial Policy

Instant Knockout Fat Burner Review: Is It Safe and Effective?

By Kelsey Masso, MS, RDN

Medically Reviewed by Natalie Olsen, MS, RDN, LD, ACSM-EP

Last Updated on August 10, 2022

Dietitian Rating:


About This Rating
The average rating of this product is calculated based on the evaluation of the following factors:
  • Support for Claims:4.1
  • Ingredient Safety:3.5
  • Customer Service:3.0
  • Value for the Price:3.8

Instant Knockout Cut is a fat-burning supplement designed to help promote weight loss through its research-backed all-natural ingredients. However, there are some important safety aspects you should consider.

Written by
Kelsey Masso, MS, RDN
Registered Dietitian
Kelsey Masso is a registered dietitian, business owner, writer, and editor with years of experience in health and wellness. She earned a Master of Science in Health and Wellness Management from Merrimack College and completed her dietetic internship with Wellness Workdays, a nationally recognized corporate wellness company.
Medically Reviewed by
Natalie Olsen, MS, RDN, LD, ACSM-EP
Registered Dietitian, Certified Exercise Physiologist
Natalie is a registered dietitian, functional medicine practitioner and certified exercise physiologist with over 15 years experience in the health and wellness industry and holds a Master's degree in Human Nutrition and Functional Medicine through a collaborative program provided by the University of Western States and the Institute of Functional Medicine.

WellnessVerge is reader-supported. When you make a purchase through links on this page, we may earn a commission. Learn More

Instant Knockout Fat Burner Review: Is It Safe and Effective?


  • Contains clinically studied ingredients
  • May aid in weight loss
  • May support energy, mood, and focus
  • Has a transparent label, showing ingredient concentrations


  • Restricted return policy with no trial period to test out the product
  • Stimulant ingredients pose a safety risk for some people

What Is Instant Knockout?

Instant Knockout is a natural fat-burning supplement that may promote weight loss through metabolism support.

This product may also help to reduce hunger and cravings, and fuel energy levels for workouts.

Instant Knockout is a product of Roar Ambition — a sports nutrition company that specializes in premium sports supplements.

Instant Knockout was developed for professional athletes in combat sports and is now backed by several boxing and MMA champions.

Even if you’re not a professional athlete, this supplement may help you reach your goals. Instant Knockout claims to help to increase metabolism and improve body composition for anyone.

Though it may work for people of all activity levels, the company discloses that the best results will be seen in active adults who maintain a healthy diet and regular exercise.

This Instant Knockout review discusses the research behind the ingredients used in this supplement, important safety considerations, and costs to help you decide if this product is right for you.

Buy Instant Knockout

Instant Knockout Ingredients

Instant Knockout is all-natural, vegan, and gluten-free. It contains the following nine main ingredients:

  • Vitamin D3: 45 mcg (1800 IU)
  • Vitamin B6: 5 mg
  • Vitamin B12: 10 mcg
  • Glucomannan (Amorphophallus Konjac): 1800 mg
  • Green Tea Extract (Camellia Sinensis): 500 mg
  • Caffeine Anhydrous: 300 mg
  • L-Theanine: 100 mg
  • Cayenne Powder (Capsicum Annuum): 100 mg
  • Black Pepper Extract (Piper Nigrum): 10 mg

Is Instant Knockout Effective? The Research Behind the Benefits

Instant Knockout uses research-backed ingredients that may help suppress your appetite while offering metabolism-boosting benefits and supporting your energy, mood, and focus.

Below, we look at the scientific evidence of the ingredients used in Instant Knockout and their role in the brand’s claimed benefits.

Reduces Body Fat

Instant Knockout claims to help reduce body fat through fat oxidation with green tea extract and the prevention of new fat cell growth with black pepper extract (piperine).

Green Tea Extract

Fat oxidation is an important part of the body’s overall fat-burning process. When the body breaks down fats through oxidation, it results in the release of energy. This energy can be used by the body for various functions. (1)

Green tea also contains antioxidants known as catechins, which are believed to promote fat oxidation. (2)

Including green tea extract in your diet may help you lose weight by increasing the amount of fat your body burns, though the evidence is limited. (2)

Research on the effective dose of green tea extract on weight loss varies.

Older studies have shown doses of 270 milligrams (mg) to 1,200 milligrams (mg) per day to be effective. (3)

A more recent study showed that 780 mg of green tea catechins may be effective for improving energy metabolism and fat loss. (4)

Instant Knockout contains 500 mg of green tea extract per daily serving, so it may provide an effective dose of green tea extract for weight loss.


Piperine — a compound found in black pepper extract — has been shown to limit the creation of new fat cells. (5)

The way it works is not yet fully understood, but it is thought that piperine blocks an enzyme that is responsible for the creation of new fat cells. (5)

There is some human research to support this.

There is no clinically agreed-upon effective dose of piperine for weight loss, but typical doses of piperine range from 5 mg to 20 mg per day. (6, 7)

Instant Knockout falls within this range, providing 10 mg black pepper extract (piperine) per daily serving.


There is evidence to support the claims that green tea extract and black pepper extract — both present in Instant Knockout — can help to reduce body fat.

Suppresses Appetite

The glucomannan in Instant Knockout may help control appetite and reduce hunger cravings.

Glucomannan is a water-soluble dietary fiber that comes from the Konjac plant.

When consumed with water, it swells up to form a thick gel inside the stomach. This gel delays gastric emptying and therefore suppresses appetite.

Ingesting glucomannan fiber may make you feel full for longer after eating, which may also help to reduce your cravings and overall calorie intake.

Studies have shown that glucomannan can help people lose weight and reduce body fat in the short term. (8)

The clinically studied dose of glucomannan is 2–4 grams (g) per day. (9, 6)

Instant Knockout only contains 1800 mg (1.8 g) of glucomannan per daily serving.


The glucomannan fiber present in Instant Knockout has been shown to increase feelings of fullness. Therefore, it may help to reduce hunger and cravings.

Boosts Metabolism

Instant Knockout may offer both a thermogenic and metabolic boost with caffeine anhydrous, cayenne pepper, and B-vitamins.

Though separately defined, a thermogenic boost (thermogenesis) is related to metabolism because it helps produce heat, and the body burns calories faster when it’s warm.

This may be beneficial for weight loss, as well as general health and wellness.

Caffeine Anhydrous

Studies have shown that caffeine consumption may help to reduce body weight, body fat, and body mass index (BMI). (10)

This may be due to its metabolism-boosting effects. Doses vary, but some studies have shown metabolic improvements with doses up to 300 mg. (11)

However, the United States Food and Drug Administration (FDA) recommends limiting caffeine intake to 400 mg per day for adults.

Instant Knockout contains 300 mg of caffeine anhydrous per daily serving, so this may be a sufficient dose of caffeine to boost metabolism for most people.

Cayenne Pepper

Capsaicin may assist with weight loss by helping to regulate metabolism, increase diet-induced thermogenesis, and decrease calorie intake. (12)

Cayenne pepper seeds contain antioxidants, vitamins, and capsaicin.

Clinical doses of capsaicin typically range from 2–6 mg per day. (13, 14)

Cayenne pepper contains about 2.5 mg of capsaicin per gram, so you would need to take at least 800 mg of cayenne pepper powder per day to fall within this range. (15)

Instant Knockout only provides 100 mg of cayenne pepper powder per daily serving, so it may not provide a sufficient dose of capsaicin to boost metabolism for some people.

Vitamins B6 and B12

Vitamins B6 and B12 are water-soluble vitamins that help to regulate metabolism, forming and breaking down nutrients in the body. (16, 17)

Both vitamins appear to be associated with lower BMI and improved body composition. (18, 19)

If you are deficient in either of these vitamins, supplementation could help your metabolism return to an average level of function.

The recommended daily amount of vitamin B6 is 1.7 milligrams (mg) and 2.4 micrograms (mcg) for vitamin B12. (16, 17)

Instant Knockout contains 5 mg of vitamin B6 and 10 mcg of vitamin B12, which is over 100% of the Daily Value for both vitamins.


Some ingredients in Instant Knockout, including caffeine anhydrous, cayenne pepper powder, and vitamins B6 and B12, may offer metabolism-boosting effects.

Supports Energy, Mood, and Focus

With caffeine anhydrous, L-Theanine, vitamin B6, and vitamin D, Instant Knockout may help support energy, positive mood, and focus to aid in your exercise performance and motivation toward goals.

Caffeine Anhydrous

When taken in average doses of 300 mg per day (equal to about 2–3 cups of coffee), caffeine has been shown to block the effects of a neurotransmitter called adenosine. (20)

This raises the amount of dopamine in the brain, which can improve mood, reduce fatigue, and increase alertness. (20)

Moderate doses of caffeine of at least 5 milligrams per kilogram of body weight may also decrease pain during workouts and reduce your perceived level of exertion — making workouts feel easier and improving exercise performance. (21)

However, this benefit appears only to be seen when caffeine is taken in a single dose, about 60 minutes before a workout.

Because Instant Knockout contains 300 mg of caffeine anhydrous per daily serving, this may be a sufficient dose of caffeine to boost energy, attention, and mood for most people.


Studies have shown that L-theanine taken at 200 mg promotes relaxation. (22)

Some people take L-theanine with caffeine with the goal of “canceling out” some of caffeine’s negative side effects.

Instant Knockout contains 100 mg of L-theanine per daily serving.

Vitamin B6

Vitamin B6 is necessary for the conversion of tryptophan to serotonin.

If someone doesn’t have enough vitamin B6, they might not be able to produce enough serotonin, which could lead to a mood disorder, such as depression. (23)

However, some older studies have not shown supplementation with vitamin B6 to prevent or treat depression. (24, 25)

With 5 mg of vitamin B6 (294% of the Daily Value) per daily serving, taking Instant Knockout could help to prevent vitamin B6 deficiency.

However, it is important not to take too much B6, so be aware of the total amount of vitamin B6 you take daily through other supplements and energy drinks. (16)

Vitamin D

Instant Knockout makes very general claims about vitamin D supplementation and exercise performance.

While Instant Knockout does not specifically claim that vitamin D can support mood, vitamin D fits under this benefit as it has been shown to reduce negative emotions. (26)

The dose of vitamin D for this purpose appears to be less than or equal to 4,000 IU/day for at least eight weeks. (26)

The effects have been more pronounced in those who have a major depressive disorder or suffer from vitamin D deficiency. (26)

Instant Knockout contains 45 mcg (1800 IU) of vitamin D3 (225% of the Daily Value) per daily serving.

Vitamin D3 has been shown to serum levels more effectively than vitamin D2, so taking Instant Knockout could help to prevent vitamin D deficiency. (27)


Evidence supports the use of some of the ingredients present in Instant Knockout — such as caffeine anhydrous, vitamin B6, and vitamin D — to improve energy, mood, and focus. In turn, this could help improve your exercise performance.

Support for Claimed Benefits

Below we rate each claimed benefit of Instant Knockout against current scientific research behind its ingredients:

Reduces body fat4.5/5
Suppresses appetite4/5
Boosts metabolism4/5
Supports energy, mood, and focus4/5

Try Instant Knockout

How to Take Instant Knockout

The recommended and maximum dosage for Instant Knockout is four capsules per day, spread throughout the day.

It is recommended to take one capsule:

  • First thing in the morning
  • Before lunchtime
  • In the afternoon
  • Before the evening meal

If you take your last dose of Instant Knockout too late at night, it could interfere with getting adequate sleep — a side effect of most stimulants.

Instant Knockout Safety and Side Effects

Instant Knockout is recommended only for adults ages 18 and over. Do not take this supplement if you are pregnant or nursing.

Instant Knockout contains green tea extract and caffeine anhydrous, which are both stimulants. Those with sensitivities to stimulants should avoid this product.

In addition, those with heart conditions or high blood pressure should not take this product.

Caffeine anhydrous is a highly concentrated form of stimulant. For this reason, it can be especially dangerous if you have a history of heart conditions. You may react differently to it than to natural forms of caffeine.

It is unclear how much caffeine is provided by the green tea extract, as caffeine content in green tea extract varies by brand.

Excess caffeine can lead to restlessness, nausea, agitation, rapid heart rate, and elevated blood pressure.

The FDA recommends limiting caffeine intake to no more than 400 mg daily (an equivalent of about three to four cups of coffee). (28)

As this supplement appears to contain multiple forms of caffeine, it is important not to exceed the maximum daily dosage.

Additionally, do not take this supplement with other products that contain stimulants or caffeine, such as coffee or tea, as this may cause you to have an unsafe intake of caffeine.

Rapid intake of caffeine of over 1,000 mg or higher has been associated with seizures and even death. (29)

Additionally, glucomannan has been associated with gastrointestinal side effects like increased belching, bloating, stomach fullness, and diarrhea - but at doses higher than what is present in Instant Knockout. (30)

In the amounts present in a daily serving of Instant Knockout, negative side effects from vitamin D3, vitamin B6, vitamin B12, L-theanine, cayenne powder, and black pepper extract are unlikely for most people.

This supplement is recommended only for adults ages 18 and over. Do not take this supplement if you are pregnant or nursing.

Be sure to consult your doctor before using this supplement, especially if you have any known medical conditions or are currently taking medications.

Instant Knockout Cost

Instant Knockout is available to purchase from the company’s official website. One bottle of the product contains 120 capsules and equals a one-month supply.

Purchase options include:

  • 1-Month Supply: $65 + $8.95 for shipping
  • 2-Month Supply: $130 + free shipping in the USA and UK
  • 4-Month Supply/Ultimate Shredding Stack: $195 + free shipping worldwide

Returns are only available for unopened and unused products. Returns must be made within 30 days of receipt in the US and within 14 days of receipt in the UK and elsewhere.

Without the chance for a trial period, this strict return policy means you must spend money to try out the product.

How Instant Knockout Compares to Alternatives

The fat burner supplement market offers a wide variety of products with different ingredients and ways in which they promise fat loss.

However, some may lack evidence to support their claims and contain potentially dangerous ingredients.

Consumers should be cautious when choosing a fat burner supplement and should always consult a doctor before starting any new weight-loss regime.


One similar alternative to Instant Knockout is Leanbean.

Leanbean is an all-natural fat burner supplement that promises to help women lose weight quickly and easily.

Similar to Instant Knockout, Leanbean claims to help boost metabolism, reduce appetite, and increase energy levels.

However, Leanbean is a low-stimulant supplement, meaning it does not contain high amounts of caffeine like many fat burners.

The main ingredients in Leanbean include:

  • Glucomannan
  • Choline
  • Vitamin b6
  • Vitamin b12
  • Chromium picolinate
  • Chloride
  • Zinc
  • Green coffee
  • Turmeric
  • Garcinia cambogia
  • Acai berry
  • Piperine

Leanbean contains a higher dose of glucomannan fiber (3000 mg) compared to Instant Knockout. However, Leanbean requires a serving of six capsules per day.

A one-month supply (180 capsules) of Leanbean costs $59.99.


Another all-natural fat burner is Skald Oxydynamic Fat Scorcher (Skald).

Like Instant Knockout, Skald claims to promote fat loss, appetite control, increased energy, and elevated mood.

The Skald product’s safety is emphasized, yet the company does not reveal the amount of each ingredient included in its product.

The proprietary (patented) blend of ingredients includes:

  • Caffeine anhydrous (110 mg)
  • N-Acetyl-Tyrosine
  • Green tea leaf extract
  • Juniper (Juniperus communis) berry extract
  • White willow bark extract
  • Verbascum thapsus leaf powder
  • Elecampane root powder
  • Bioperine black pepper fruit extract

Skald only requires a serving of two capsules per day.

A one-month supply (60 capsules) of Skald can be purchased for $49.00.


There are other all-natural fat burner supplements available that offer a few similar ingredients and claim similar benefits to Instant Knockout for a comparable price.

The Bottom Line

Instant Knockout may be a promising fat-burning supplement with all-natural ingredients backed by solid research that may aid in weight loss by reducing body fat, suppressing appetite, and boosting metabolism.

It may also support your energy, mood, and focus — helping you improve your athletic performance and reach your goals.

If you are an active adult looking to lose weight faster, this could be a safe fat-burning supplement to use in combination with a healthy diet and lifestyle.

Still, it is best to check with your doctor before trying this supplement, especially if you may be sensitive to stimulants like caffeine or have certain medical conditions, such as heart issues.

Dietitian’s Tip

Weight loss supplements are only intended to support — not replace — a healthy diet and active lifestyle.

Changing your diet and increasing your physical activity are crucial if your goals are to improve your exercise performance, body composition, and overall health.

Making the shift toward a plant-based diet may be helpful.

Focus on fruits, vegetables, lean proteins, whole grains, and healthy fats. This way of eating can help support your metabolism by providing the nutrients your body needs to function at its best.

Also, it may be helpful to include foods that promote fat oxidation in your diet. Foods that are rich in antioxidants — such as fruits and vegetables — are good choices for promoting fat oxidation.

Try incorporating regular strength-building and cardiovascular activities for a minimum of 150–300 minutes per week to help you reach your goals.

Shop Instant Knockout
Instant Knockout may be an excellent option to add to your current exercise and healthy nutrition routine. It uses research-backed ingredients that may help with weight loss, boost metabolism, and support energy, focus, and mood.
Was This Article Helpful?YesNo
Thanks for your feedback!
In a few words, please tell us how this article helped you today.
Please let us know how we can improve this article by selecting your concern below.
Thank You! We appreciate your feedback.
* Please select at least one topic:
Please Note: We cannot provide medical advice. This feedback will help us continue improving your user experience on WellnessVerge.
Please Note: We cannot provide medical advice. This feedback will help us continue improving your user experience on WellnessVerge.
Submit Feedback
Submit Feedback

At WellnessVerge, we only use primary references for our articles, including peer reviewed medical journals or well-respected academic institutions.

  1. Understanding the factors that effect maximal fat oxidation | Journal of the International Society of Sports Nutrition | Full Text:
  2. The Effect of Green Tea Extract on Fat Oxidation at Rest and during Exercise: Evidence of Efficacy and Proposed Mechanisms – ResearchGate:
  3. Antiobesity effects of green tea catechins: a mechanistic review - PubMed:
  4. Influence of green tea catechins on oxidative stress metabolites at rest and during exercise in healthy humans – ScienceDirect:
  5. Piperine, a Component of Black Pepper, Inhibits Adipogenesis by Antagonizing PPARγ Activity in 3T3-L1 Cells:
  6. A Comprehensive Review on Pharmacotherapeutics of Herbal Bioenhancers - PMC:
  7. Curcumin and Piperine Supplementation and Recovery Following Exercise Induced Muscle Damage: A Randomized Controlled Trial - PMC:
  8. The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials - PubMed:
  9. Glucomannan and obesity: a critical review - PubMed:
  10. The effects of caffeine intake on weight loss: a systematic review and dos-response meta-analysis of randomized controlled trials:
  11. The effect of caffeine on energy balance:
  12. Chili pepper as a body weight-loss food:
  13. Effects of novel capsinoid treatment on fatness and energy metabolism in humans: possible pharmacogenetic implications - PMC:
  14. Acute Effects of Capsaicin on Energy Expenditure and Fat Oxidation in Negative Energy Balance - PMC:
  15. Determination of Capsaicin and Dihydrocapsaicin in Capsicum Fruit Samples using High Performance Liquid Chromatography - PMC:
  16. Vitamin B6:
  17. Vitamin B12:
  18. The Effect of Pyridoxine Hydrochloride Supplementation on Leptin, Adiponectin, Glycemic Indices, and Anthropometric Indices in Obese and Overweight Women - PMC:
  19. Inverse Association Between Serum Vitamin B12 Concentration and Obesity Among Adults in the United States - PMC:
  20. Caffeine increases striatal dopamine D2/D3 receptor availability in the human brain - PMC:
  21. Acute caffeine ingestion enhances strength performance and reduces perceived exertion and muscle pain perception during resistance exercise:
  22. In Search of a Safe Natural Sleep Aid - PubMed:
  23. Depression and Vegetarians: Association between Dietary Vitamin B6, B12 and Folate Intake and Global and Subcortical Brain Volumes - PubMed:
  24. Vitamins B12, B6, and folic acid for onset of depressive symptoms in older men: results from a 2-year placebo-controlled randomized trial - PubMed:
  25. The role for vitamin B-6 as treatment for depression: a systematic review - PubMed:
  26. The effect of vitamin D supplement on negative emotions: A systematic review and meta-analysis - PubMed:
  27. Vitamin D - Health Professional Fact Sheet:
  28. Caffeine | The Nutrition Source | Harvard T.H. Chan School of Public Health:
  29. The clinical toxicology of caffeine: A review and case study:
  30. Glucomannan – Drugs.com: