Instant Knockout vs Stacker 2 Fat Burner [Only one Is Effective!]

Instant Knockout vs Stacker 2 Fat Burner

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Instant Knockout vs Stacker 2 Fat Burner

When it comes to fat burning supplements the first thing to look for is a safe formula. Can either product in our Instant Knockout vs Stacker 2 Fat Burner review give us a great product that ensures our safety?

This isn’t always the case and way too many companies fall down in this area.

It isn’t the only thing we are concerned with though. The best product is also going to be the most effective. Any product that can do the following has a chance of impressing:

  • Burn fat effectively
  • Be safe
  • Suppress appetite
  • Increase energy

So, which of these is the best option? Let’s start by getting to know the companies a little better first.

Instant Knockout vs Stacker 2 Fat Burner: Who Makes These Products?

Roar AmbitionInstant Knockout Review

Our first company is the UK based team behind Instant Knockout.

With a load of before and after profiles appearing online, their products seem to be a favorite among many. We like that they review and amend their ingredient profiles regularly. This means their customers are getting the most up to date version possible.

Instant Knockout comes with a big 90 – day money back guarantee. This really gives you the chance to try it on for size, and also means purchasing is risk-free!

If endorsements impress you then UFC fighter Diego Sanchez puts his name to Instant Knockout. He uses it to make weight before a bout.

They are also the company behind the T Booster TestoFuel. Former Mr. Universe Robby Robinson puts his name to it.

NVE PharmaceuticalsStacker 2 Fat Burner

From the UK to the USA for our second company.

They claim to be the company behind the world’s strongest fat burner. The Stacker 2 brand has been going since 1997.

They actually use the fact that this is ephedra free as a selling point. Since the banned substance has potential side effects you would want to avoid, this is only a good thing.

They gave a string of places that their products may have been seen including the UFC, Fox News, NBC and more.

We like that they offer free shipping for orders over $50 but we couldn’t see any money back guarantee.

One place you will find their products is Amazon. This is becoming more common in the industry but there are still plenty of supplement brands that choose not to sell on there. A lot of the time this is because they don’t want theirs to be listed alongside some of the low-quality products on there.

Instant Knockout vs Stacker 2 Fat Burner Ingredients

Now we can really see which is going to be more effective. The early signs aren’t great for Stacker 2. They have included all but one ingredient in a proprietary blend. This means we don’t get to see exactly what goes into each serving.

The serving suggestions are both good though. The advice of Instant Knockout is one capsule 3-4 times a day. Stacker 2 Fat Burner, one capsule 3 times a day. Both will spread out the fat burning benefits.

Mutual Ingredients

Green Tea Extract

An excellent start from both products, this is up there with the best ingredients for a fat burner.

A thermogenic, it heats the body up on the inside, causing it to burn fat to cool itself down again. The catechins are what is really beneficial. These act as antioxidants and help to fight against disease. They even help the body when it comes to weight management. supports this by saying they are anti-obesity and anti-diabetic which makes this ingredient even more impressive.

It is an ingredient that even has links to increased endurance levels.

WebMD advises that it is a milder stimulant than Caffeine Anhydrous and contains just 2-4% Caffeine. The added focus and alertness are just two things you gain from this.

The 500 mg in Instant Knockout is an excellent dosage. The fact that it finds itself in a proprietary blend that totals 801 mg over 3 servings with 4 other ingredients means it is unlikely to be dosed as well.


Another top ingredient.

The energy boost is one of the primary attributes. If you are finding yourself using a fat burner alongside a diet that restricts calories, it will be really useful.

The sped up metabolism will also help to burn fat and it is such a good all-rounder you can find it in other supplements like nootropics and pre-workouts.

The version in Instant Knockout is Caffeine Anhydrous. This is a powdered version that is easily absorbed.

We like the dosage in Instant Knockout. 350 mg over 4 servings means it will really work, but also be well tolerated as it is spread out.

Stacker 2 hasn’t been so sensible. Their dosage of 200 mg per capsule means anyone taking the 3rd capsule is consuming 600 mg of Caffeine.

This isn’t advisable and really puts you in the category that is at risk of potential side effects. With Caffeine, these include anxiety, insomnia, jitters, high blood pressure, irritability, upset stomach and more.

Individual Ingredients

Instant Knockout


An effective start to their ingredients.

Glucomannan is a dietary fiber that works as an appetite suppressant. It manages to do this by absorbing water and swelling in the stomach. This makes the user feel full and means you are less likely to reach for a snack between meals.

The 500 mg is another big and effective dosage that will really help.


Another great ingredient.

WebMD says it can decrease LDL (bad cholesterol) levels in people who have lower blood fat levels.

There are studies that show it is able to communicate with the brain to tell it that the body is full. This means we already have two effective appetite suppressants.

The 100 mcg is all you need.

Cayenne Powder

Another favorite here at CLM.

It works in two of the best ways a fat burner should. It is another thermogenic meaning it will have you burning even more fat as you rest.

WebMD tells us that Cayenne Pepper is also good for appetite suppression. They say that it has been found to curve appetite, especially in those who do not already eat spicy foods.

The 100 mg is another optimal dosage.

Black Pepper Extract

A popular ingredient in these type of supplements.

It enhances the capabilities of other nutrients making it a good one if the others are proven fat burners.

Instant Knockout so far is full of great ingredients making Black Pepper Extract a good idea.

Green Coffee Bean Extract

Another proven ingredient.

Green Coffee Extract is coffee before the color has been roasted out. Also, before most of the chlorogenic acid has been as well.

It is this that stops us from storing as much fat and keeps blood sugar levels down.

WebMD talks of a study that looked into adults with obesity found that taking Green Coffee Extract for between 8 to 12 weeks resulted in more weight loss for those when compared to others taking a placebo.

At 100 mg Instant Knockout have included a good amount.

Vitamin B6

Another sensible inclusion, it works like many of the B-vitamins to help the body to make energy from food.

It converts it into glucose so it can then be used for energy. The 5 mg included is another good dosage and B6 also has metabolism boosting links.

Vitamin B12

Similar to the previous ingredient only it stops us from storing as much fat as well.

B12 isn’t something our bodies create naturally so getting the benefits from a supplement is a good idea.

Some of the more common sources are meat, dairy, and fish so vegetarians and vegans will really benefit from supplementing it.


Zinc has backing for being able to enhance the mood of the consumer according to

Also, it is another ingredient that stops us from storing as much fat.

The 10 mg is another optimal dosage.

Stacker 2 Fat Burner

Yerba Mate

Because of the Caffeine content, it can be of use.

It is a thermogenic ingredient. We already know why this is good but it is nice to see this supplement giving you more of this trait as well.

Yerba Mate also acts as an appetite suppressant. advises that it has not been shown to be a more effective fat burner than compounds like Green Tea Catechins, though it can help reverse some of the adverse health effects associated with obesity.

What the trustworthy resources say is that it doesn’t appear to be as potent or as useful as other fat burner ingredients but even if the effects are minor, it seems to help.

Still, you want to know the dosage to see how good it could be.

Guggulsterone Gum Extract

The first truly disappointing ingredient really.

It is best summed up by who say that this has been investigated for their usage in elevating thyroid function, but with lackluster results.

To add to this, WebMD is not impressed. They advise that Guggulsterone Gum Extract is commonly used for weight loss in people who are obese or overweight. But there is limited scientific research to support these uses.

Still, research exists that shows that when it was taken with a string of other ingredients, along with an exercise program and restricted calories it helped people to lose weight slightly. Still, there is limited evidence to suggest that it can achieve this on its own.

Also, eating less and exercising more does help you lose weight, there’s nothing to say that this ingredient helped directly.

We don’t even know how much room it is taking up as the dosage isn’t provided.

Cassia Nomame Plant Extract

A potentially useful ingredient even if it isn’t the most common in a fat burner.

WebMD advise that people take it by mouth for weight loss. It is thought to work by preventing the body from absorbing dietary fat. WebMD says this causes fat to be excreted in the feces, which might help promote weight loss in some people.

They also go on to tell us that its uses and effectiveness for weight loss have ‘insufficient evidence for’.

Like with any understudied ingredient, there isn’t a lot known about the dosage needed for a true effect.

White Willow Bark Extract

It’s a bit of a whimper to end on for Stacker 2.

It works in a similar way to Black Pepper Extract but since this supplement does have enough impressive ingredients, it is a little unnecessary.

White Willow Extract actually works in a similar way as Aspirin. It can alleviate pain which would be great if this is what we are after.

Keep an eye out for potential side effects, WebMD says these can include itching, rash, and allergic reactions, as well as an upset stomach. WebMD does continue that it is likely to be safe, but not when taken for longer periods.

In terms of fat loss, we want to know the dosage to see if it can help.

Instant Knockout vs Stacker 2 Fat Burner Side Effects

The easy place to start is with Instant Knockout.

Their ingredients are natural, and dosages effective, yet completely safe.

The same cannot quite be said for Stacker 2 though. Their ingredients, on the whole, are safe, but it is the Caffeine dosage that is a worry.

By giving you 600 mg it puts you at risk of potential side effects such as insomnia, jitters, anxiety,  upset stomach, high blood pressure, irritability and more.

Instant Knockout vs Stacker 2 Fat Burner Pros and Cons

Instant Knockout Pros

  • Natural ingredients
  • Money back guarantee
  • Used by top athletes
  • Ships worldwide
  • Enhances metabolism
  • Suppresses hunger

Stacker 2 Fat Burner Pros

  • Green Tea Extract a good ingredient
  • Serving schedule is good

Instant Knockout Cons

  • Not available in store
  • Shouldn’t take too late in the day because of the caffeine levels

Stacker 2 Fat Burner Cons

  • Proprietary blend
  • Too much Caffeine
  • Ineffective ingredients

Instant Knockout vs Stacker 2 Fat Burner Conclusion

Winner: Instant Knockout

Buy Instant Knockout from:

(Clean Lean Machine tip: Get 1 box free when you buy 3 boxes!)

It was easy to go with the more reliable fat burner today.

Instant Knockout stood out, as it often does because of its selection of natural and effective ingredients that have the backing of several studies.

The dosages are also very generous. They chose not to just stuff it full of stimulants like so many companies do. With a sensible yet effective amount of Caffeine, appetite suppressants, thermogenics, and metabolism boosters, it ticks every box.

It is easily the best option for anyone serious about burning fat.

Buy Instant Knockout from:

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