Stacker 4 is an ephedra-free fat burner made in America by NVE Pharmaceuticals, Inc. and distributed under the Stacker 2 brand name.

NVE Pharmaceuticals is a respected private label manufacturer that’s been active in the supplement industry for over 30 years. It launched its Stacker 2 brand in 1997. Stacker 2 Fat Burner was its flagship product and it became very popular in the US, the Netherlands, and many other countries.

The Stacker 2 brand takes its name from the bodybuilding term “stacking.”

Stacking is when bodybuilders use (stack) two or more supplements or steroids alongside each other.

Back in the late 90s, a combination of ephedra, caffeine, and aspirin was quite a popular stack. Not surprisingly, ephedra was a key ingredient in the original Stacker 2 supplement, which was designed to function as a one-pill stack.

Ephedra is a herb that provides the stimulant ephedrine, which is linked to serious side effects. The FDA was so concerned about the negative effects, it banned ephedra products in 2003.

The ban was overturned the following year and then reinstated in 2006.

Stacker 2 products no longer contain ephedra but due to the brand’s strong connection to the herb, Stacker 4 Fat Burner is marketed as ephedra-free.

According to the label, Stacker 4, is the “most popular and best sold Stacker product.” However, at the time of this review, Stacker 4 was no longer available via the Stacker 2 website. It’s still readily available in the Netherlands though and is becoming easier to obtain in the UK.

Although Stacker 4 Fat Burner does not contain ephedra, it is still very much a stimulant-driven product that provides 300 mg of caffeine anhydrous per capsule ‒ plus caffeine from other sources. It’s likely to excel as an energy provider but is probably too extreme for the average person looking for a good fat-burning diet pill.

I will suggest a good alternative to Stacker 4 Fat Burner at the end of this review.


Promised Benefits

  • Supports the goals of athletes focusing on body composition
  • 300 mg of caffeine per capsule to increases focus and alertness


How Does Stacker 4 Work Fat Burner  Work?

Like most fat burners, Stacker 4 is designed to boost metabolism. The problem is, it’s overly reliant on stimulants to do it.

When metabolism increases, you burn more calories per hour. This can improve your weight loss results but you will still need to control how many calories you consume in a day.

Stimulants are good for providing energy. They improve mental focus as well, but none of the top diet pills use them in overly high amounts.


Things to Bear in Mind

Like other weight management products, Stacker 4 Fat Burner is a supplement. It’s important to understand what a supplement is and never to see any form of supplement as a magic pill.

The word “supplement” refers to something you get or use in addition to something else. For instance, Some people work two jobs to “supplement” their income.

Diet pills and other weight loss supplements, supplement the efforts you are already making by controlling your diet.

In this case, it’s important not to see Stacker 4 as a product that provides an excuse not to try and eat healthy foods. The pills will work best if you use them alongside a healthy diet that contains nutritious foods that are low in fat and sugar.


List of Ingredients in  Stacker 4 Fat Burner

Each Stacker 4 capsule has seven ingredients in it. Six of them are included as a proprietary blend that accounts for just under half the capsule content. The main ingredient is caffeine.

One capsule provides:

Caffeine Anhydrous (300 mg)
Proprietary Blend (250 mg)

Consisting of:

  • Green Tea Extract
  • Yerba Mate
  • Guarana
  • Capsicum
  • Kola Nut
  • Siberian Ginseng

Stacker 4 Fat Burner Ingredient Potential

Okay, we’ve reached a very important point in this Stacker 4 Fat Burner review. It’s time to take a closer look at the ingredients and see what they can do.

In this case, the lack of inclusion rates presents some problems. It’s a great pity there is no way to be certain of the ratios in the proprietary blend, but that’s the way it is.


​Caffeine Anhydrous (300 mg)

Caffeine anhydrous is a caffeine concentrate. Although it comes from natural sources, it’s highly refined.

This form of caffeine powder is an extremely popular supplement ingredient. It’s good for providing quick energy because it enters the system pretty fast.

Caffeine’s abilities as a stimulant are also useful for boosting focus and concentration. You probably know plenty of people who drink coffee to wake themselves up in the morning or fight feelings of fatigue.

Caffeine is also a proven fat burner. Many studies prove its ability to support weight loss by boosting metabolism.

The results of one study suggest caffeine may offer more benefit to people who are not overweight than it does to those who are obese. The average Stacker 4 user is likely to be too active to be obese. This could make caffeine a particularly appropriate inclusion but the dose provided is still worryingly high.


Green Tea Extract (Quantity Unknown)

Green Tea: One of the ingredients in Stacker 4 Fat BurnerThe antioxidants in green tea (green tea catechins) support fat loss by boosting metabolism and thermogenesis. By doing so, they help you to burn extra calories while you are training. Green tea catechins also help you to burn extra calories while you are taking it easy or fast asleep.

There’s a mountain of research that proves green tea’s prowess as a fat burner and one study suggests the benefits it provides may last for up to 24 hours.

Green tea catechins are also good at reducing levels of free radical toxins within the body. This is one of the main reasons green tea has a reputation for being the healthiest beverage in the world.

The problem with Stacker 4 is, there is no way to be certain the formulation contains a decent amount.


​Yerba Mate (Quantity Unknown)

Yerba mate is a plant. In South America, people use its leaves to make yerba mate tea.

Yerba mate is very popular and in several countries, it’s deeply ingrained in the culture. I’m not sure how it works in other South American countries but, in Uruguay, adolescents are given a yerba mate gourd (drinking vessel) as a gift to mark their coming of age.

Yerba mate tea gets a lot of praise for its ability to boost energy and improve mental focus. But that won’t come as a surprise when I tell you Yerba mate is a source of caffeine.


​Guarana (Quantity Unknown)

Guarana is a tropical berry. It’s a popular supplement ingredient and is also present in certain energy drinks. Manufacturers use guarana because it’s a potent source of caffeine.

Unlike other alternatives, guarana releases caffeine into the body quite slowly. Supplements that provide it are generally better for delivering longer-lasting stimulation.

Guarana’s natural slow-release mechanism, also makes it less likely to cause side effects. This is because it does not dump a lot of caffeine into your system all at once.

However, regardless of whether the dose is low or high, in this case, guarana’s presence adds an extra dose of caffeine to a supplement that already has an unusually high amount.


​Capsicum (Quantity Unknown)

Capsicum Peppers (Red, Yellow, and Green)Capsicum peppers provide a compound called capsaicin. Cayenne (chili pepper) is a member of the capsicum family too and is an equally good source of capsaicin.

A lot of research proves the capsaicin provided by capsicum fruits can help people to lose weight.

Capsaicin usually gets the most attention for its ability to increase metabolism and thermogenesis. Most of the top fat burners provide some capsicum or cayenne.

Although there are plenty of studies that prove the fat-burning capabilities of capsaicin, to avoid flooding this page with links, I’m only going to provide one:

Research shows capsaicin also functions as a hunger suppressant, so it’s not surprising it’s become such a popular diet pill ingredient.

Again though, it would be good to know how much capsicum Stacker 4 provides.


​Kola Nut (Quantity Unknown)

Kola nuts are not nuts at all. They are the seeds.

Kola nuts were a key ingredient in the original Coca-Cola formula but you won’t find them in the present drink. They are often included in supplements though. Manufacturers use them because they are a good source of caffeine.


​Siberian Ginseng (Quantity Unknown)

Ginseng is one of the most respected and well-known medicinal herbs in the world. However, although the name suggests otherwise, Siberian ginseng (Eleutherococcus senticosus) is not a true ginseng. It is a distant botanical relation though.

These days, the herb is more commonly known as “eleuthero.” This helps prevent it from being confused with true ginseng (Korean/Panax Ginseng).

Eleuthero has a long history of use in traditional herbal medicine, but it’s not as potent as Korean ginseng.

The Stacker 4 marketing material does not explain eleuthero’s role in the formulation but, like similar adaptogen herbs, one of the things it’s good for is protecting against stress. (


How Good is Stacker 4 Fat Burner?

If you are looking for a supplement that can increase your energy and mental focus while training, unless you have an unusually strong tolerance to stimulants, Stacker 4 should do the trick.

However, each pill provides more caffeine than you would get if you drank three standard cups of coffee back to back or knocked back a quadruple espresso. That’s a lot of stimulation. It’s likely to be too much for the average man or woman to handle and the chances of jitters, nausea, or other caffeine-related side effects are quite high.

If you can handle all that caffeine and feel the benefits, Stacker 4 could be a useful product but your body will probably adapt over time, causing the benefits to diminish.

Can Stacker 4 help you to burn more fat? Absolutely. There’s no way to be certain what quantities of green tea and capsicum are involved, but it seems likely there should be enough to provide a metabolism boost.

Even if the quantities are insufficient, the caffeine should be able to provide most people with a decent metabolism boost. However, its ability to do this will be impaired if your tolerance to stimulants is high.


How to Use Stacker 4 Fat Burner

The dose is one capsule, taken after a meal. The usage guidelines warn against taking more than three capsules per day.

My advice would be to stick to one capsule per day and to leave 4-5 hours between doses if you don’t.

If it’s one of your workout days, it may be beneficial to take the capsule 30-60 minutes before training.

Unless you are overly used to stimulants, doing so should help you enjoy a better workout and burn extra calories while you train.

However, if you normally workout in the evening, taking a dose late in the day could interfere with your ability to sleep.

To be honest though, if I were going to use a product like this, I’d discuss my intentions with a doctor first and I suggest you do the same.

Health Considerations

If you are pregnant or nursing a child, please don’t take any kind of supplement without getting clearance from your doctor first.

If you have an existing medical condition of any kind at all, it would also be unwise to use supplements without checking with your doctor first.

Certain supplement ingredients can present interaction issues when combined with medication. It doesn’t matter if the medication has been prescribed by a doctor, a dentist, or another medical professional. If you are taking medication, don’t use it with supplements without asking a doctor first.

*Information on the Diet Pill Ninja website is not intended to be a substitute for professional medical advice.


Stacker 4 Fat Burner Customer Reviews

There is plenty of customer feedback for Stacker 4 Fat Burner. Many of the customer reviews are written in Dutch or other European languages but, with modern-day translation tools, that’s not really an issue.

Most of the reviews are very praising and suggest Stacker 4 works well as an energy provider. Some reviews mention weight loss too, but the average Stacker 4 user appears to place greater value on the supplement’s ability to provide mental and physical stimulation.

Not surprisingly, some of the positive reviews say Stacker 4 Fat Burner takes a little time to get used and there are reports of racing heart rate, jitters, and similar stimulant-related side effects. However, the average user appears to be happy to bite the bullet and give their bodies time to adapt.

The people who give Stacker 4 Fat Burner a low rating and say they noticed little or no difference may have experienced the lack of results due to an unusually high caffeine tolerance. This is something many Stacker 4 users could build up over time.

Let’s take a look at a couple of positive comments from customers.

Stacker 4 Fat Burner: Positive Customer Reviews
(These Customer Reviews Were Translated from Dutch Using Google Translate)



Here are two comments from customers reporting a poor experience.

Negative Customer Review (Stacker 4 Fat Burner)
(These Customer Reviews Were Translated from Dutch Using Google Translate)


Does Stacker 4 Cause Side Effects?

Stacker 4 is a high-caffeine supplement so some people using it will get side effects.

However, a lot of people who buy Stacker 4 have years of experience with stimulant-rich products and have built up a tolerance that protects them from side effects.

Unless they are a seasoned coffee junkie, the average person seeking help to lose weight is unlikely to have such a high tolerance so they could get a nasty surprise after they take the first pill.

If there are any negative issues, it may take up to six hours before the effects wear off.

Caffeine side effects may include:

  • Insomnia
  • Jitters
  • Restlessness
  • Headaches
  • Nausea
  • Dizziness
  • Anxiety
  • Dehydration
  • Rapid/abnormal heart rhythm

According to Medline Plus (trusted source), It’s not harmful for most people to consume up to 400 mg of caffeine per day. However, people who get this much from caffeinated beverages will receive it in smaller doses, throughout the day. Stacker 4 Fat Burner provides 300 mg in a single pill and most of it is likely to be absorbed within an hour.

The chances of side effects will increase considerably if you drink coffee, energy drinks, or other caffeinated products while using this product.

(Further Information About Caffeine from MedlinePlus)


The Best Place to Buy Stacker 4 Fat Burner

Bottle of Stacker 4 Ephedra-Free Fat BurnerThe best place to buy this product is going to be largely dictated by your geographic location. Stacker 2 is based in the USA, so I would normally advise people who are based in North America to buy Stacker 4 Fat Burner via the official website.

Unfortunately, the product no longer appears to be on sale via the site and I have to wonder if it may be going to be discontinued.

The strange thing is, Stacker 2 is still on sale. This is surprising if Stacker 4 is currently the “most popular and best sold Stacker product.”

At the time of this review (July 2021), I was unable to find Stacker 4 available at Walgreens, Walmart, or any other online retailers based in the USA but it’s still readily available in Europe.

It’s also possible to buy Stacker 4 from the GymRat website in the UK. Expect to pay around £25 per bottle, plus shipping.

Each bottle of Stacker 4 contains 100 capsules so the price is not bad at all but you need to be aware Stacker 2 does not provide a money-back guarantee. At the end of this review, I’m going to suggest an alternative option that does.


Stacker 4 Fat Burner Review: Diet Pill Ninja Conclusion

The Diet Pill Ninja: Honorable Diet Pill ReviewsI’m going to end this review by saying Stacker 4 Fat Burner is not a supplement I would take myself. I don’t like the idea of taking such a big caffeine hit all at once, even though my tolerance is unusually high (I love my coffee).

However, if you are used to taking supplements that are so stimulant-rich and are set in your ways, you may find you and Stacker 4 are a good match. Just bear in mind you may find the benefits you feel may reduce over time and constantly seeking stronger products is a very slippery slope.

First and foremost, this is a diet pill review site. If you have come here because you need help to lose weight, I do not recommend Stacker 4.

Weight loss is often a long process. If you need the help of a supplement, you may continue to need it for quite some time. There are alternative options that can offer you a greater level of support, without presenting the same risk of side effects.


Phentaslim: A Good Alternative to Stacker 4

Bottle Vegan-Friendly PhentaslimIf you were considering using Stacker 4 and this review has encouraged you to change your mind, suggest you consider using Phentaslim instead.

Phentaslim costs slightly more per bottle than Stacker 4, but there are no shipping charges to worry about and the manufacturer offers a 60-day money-back guarantee.

It’s also possible to take advantage of bulk-buy discounts that bring down the cost per bottle. Bearing in mind the lack of shipping charges, the cost of using Phentaslim Vs. Stacker 4 over a few months could be more or less the same.

Like Stacker 4  Fat Burner, Phentaslim tends to appeal to a lot of people who like to hit the gym and are working hard to achieve their perfect body.

Phentaslim contains caffeine but less than Stacker 4 and it’s delivered over three doses per day instead of hitting the body all at once. Like energy drinks, Phentaslim also provides B vitamins to help your body get extra energy from food.

The company that makes Phentaslim provides all the ingredient inclusion rates and two of the ingredients are green tea and cayenne. Both are included in respectable doses.

Again, as with Stacker 4 Fat Burner, Phentaslim contains ginseng. It’s included in a very generous dose and it is Korean ginseng, not the Siberian impostor.

Phentaslim provides several more useful ingredients as well, including zinc, which supports improvements in muscle growth by boosting testosterone.

Buy Phentaslim               Read My Phentaslim Review

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