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Stacker 2 Review - Does This Fat Burner Work? Are side effects and questionable results deal breakers?

By Summer Banks on Sep 02, 2016
Stacker 2 Review

Diet products either work or they don’t. Period. Let’s find out which one Stacker 2 is. We looked at the ingredients, side effects, customer service and clinical research. Furthermore, we examined hundreds of user reviews and comments. Then, we summarized and condensed to give you the bottom line.


What is Stacker 2?

First off, Stacker 2 is a fat burner using the principles of the infamous ECA Stack. The ingredients are kola nut, yerba mate, cassia mimosoides, white willow bark, caffeine, green tea, guggulsterones and gymnema. You’ll take one to three per day after meals. The blister pack makes it easy to take with you on-the-go.

Stacker 2 was brought to the market more than 20 years ago by NVE Pharmaceuticals. It’s available in at local stores and through the official website. We like it contains a few natural ingredients and it appears to be affordable, but read on…

Side-Effects – “Look Out?”

The first concern was the intensity of Stacker 2 side effects. “This one contains multiple fat burners,” said our Research Editor.  “While they’re supposed to boost metabolism, there’s a chance you could experience adverse reactions..

“I noticed it also made me jittery and sometimes gave me a headache,” said one user.

“Even after doing intensive workouts I still had too much energy. I had to stop taking them, because occasionally I had caffeine crashes. They are not fun at all,” offered another.

Side effects are rare, so we found some users that didn’t experience adverse reactions.

“No headache, jitters or anxiety like other caffeine pills,” commented a dieter.

Results – “No Weight-Loss!”

Based on some Stacker 2 reviews, there’s were customers that didn’t notice results. “I did not experience any weight loss on this product. I did have more energy but I was looking for a fat burner,” said one customer online.

“The pill does give a great amount of energy, but the claim of it being a fat burner is bogus,” said a user.

Upon reading further reviews, some customers noticed results. “I tried them again and they helped me weight,” explained a customer.

“After the first one, I felt warm and could tell my metabolism was increasing,” stated another.

Our research has shown if there is some particular part of a diet supplement that’s troublesome, like not producing results, the likelihood of long-term success is slim. If Stacker 2 doesn’t help you lose weight or burn fat, is it really worth it?

The Science – “Legitimate?”

Some of the Stacker 2 ingredients have been clinically verified to work. The white willow bark extract, green tea extract and kola nut are common ones that have been shown to be mildly effective. However, the any results aren’t connected to this formula. We at DietSpotlight find clinical research to be important to the review process. When there’s no solid-science used to support the claims, we have concerns.

The Bottom Line – Does Stacker 2 Work?

Will Stacker 2 help you lose weight? Well, we like that it contains  few natural ingredients and that we found some positive customer comments, but the lack of research showing it works is concerning. Also, reports of negative side effects and no real results leaves us a bit skeptical about giving it the thumbs up.

If you are still in the market for an effective fat burner, we suggest going with one that’s clinically proven to work, without any mentions of harmful side effects.

Among the best products we’ve seen in 2016 is one called Leptigen. It’s a blend of four fantastic ingredients proven to help boost metabolism and burn fat. Thankfully, it has been tested in scientific studies and verified by clinical research. Upon reading user reviews online, we haven’t found any side effects, but we did find plenty of reports of dieters seeing fantastic results.

The makers of Leptigen are even offering a Special Trial Offer – always a good sign, in our opinion.

Get Your Sample Today »
About the Author:

Summer Banks has researched over 5000 products in the past 10 years. She has years of nursing training, experience as a manager responsible for 15 supplement brands, and completed coursework on Food and Nutrition from Stanford University. full bio.

How Does Stacker 2 Compare?

Previous Stacker 2 Review (Updated March 19, 2014):

What You Should Know

Click Here To See Our Highest Rated Review

Stacker 2 derives its name from the term "stack" or "ECA stack". ECA is an acronym for ephedrine, caffeine and aspirin. When "stacked" or combined correctly it is said to be a fat burner and energy booster. Originally, this product contained ephedrine. The ephedrine has been substituted with a combination of ingredients, called a Proprietary Formula, that supposed to work similar to ephedrine. The official website of NVE Pharmaceuticals, the maker of the product, sells only the ephedrine free version. Be aware that Stacker 2 with the ephedrine formula is still being sold on online stores all over the web.

The official NVE Pharmaceuticals website is attractive if you like flash and sexy videos. The company manufactures and markets a variety of weight loss products and energy drinks. To obtain product information much beyond an ingredients list one has to go elsewhere. The product is inexpensive, less than $20 for a hundred tabs, and available at discounts and in a variety of quantities.

List of Ingredients

Kola Nut - The usual source of caffeine in stack formulas.

Yerba Mate - Rumored to help in weight loss, no quality evidence.

Cassia Mimosoides - As a lipase inhibitor it theoretically prevents the body from absorbing and storing fat.

White Willow Bark - The usual source of aspirin in stack formulas.

Caffeine Anhydrous - Mild thermogenic benefit and energy booster.

Green Tea - Proven fat burning and thermogenic benefits in sufficient quantities.

Guggulsterones - Stimulates thyroid and thereby may increase metabolism.

Gymnema - Historically used to treat diabetes. May inhibit taste for sweets.

Product Features

Stacker 2 claims to be "The World's Strongest Fat Burner". The formula, called a "Proprietary Blend", is designed to increase your metabolism and therefore your body heat. Be it a proprietary blend or not, many of these ingredients are common in fat burners like Instant Knockout. This stimulates your brain and raises your heart rate. White willow bark is essentially aspirin and the caffeine completes the stack. In addition to weight loss, benefits claimed are a decrease in appetite and an increase in energy.

See Our Featured


  • Inexpensive.
  • Ephedrine free.
  • Contains ingredients proven to be helpful in weight loss.


  • Claims to be free of side effects while containing ingredients commonly known for its side effects, such as caffeine.
  • Does not break down the quantities for individual ingredients making it difficult to judge whether sufficient amounts are present to be effective.
  • Without ephedrine, there is no evidence that the product will work like a traditional "stack" or "ECA stack" product.
  • The importance of diet and exercised is not highlighted.
  • No before and after photos or testimonials.
  • No guarantee.


Stacker 2 has a few quality positive weight loss ingredients combined with ingredients that are not likely to do anything at all. It is assumed that the Proprietary Blend is greater than the sum of its parts. There is no evidence whatsoever to support that claim. When fad ingredients are involved, like in Batch 5, dieters often report ineffectiveness. It's impossible to measure the potency of the product or determine if there is enough of the ingredients to be effective. If you have had success with traditional "stack" products in the past, you will be disappointed with Stacker 2.

Stacker 2 Questions & Answers:

We summarized hundreds of user comments about Stacker2 into this helpful FAQ.

What are the side effects of Stacker2?

Some Stacker 2 side effects may include anxiety, nervousness, jitteriness, increased heartrate, irritability, sleeplessness, upset stomach, headaches and shortness of breath.

What are the ingredients in Stacker2?

Stacker 2 ingredients are yerba mate, caffeine, green tea leaves, guggulsterone, cassia mimosoides extract, white willow bark, gelatin, stearic acid, magnesium stearate, titanium dioxide, dibasic calcium phosphate, microcrystalline cellulose, fd&c yellow #5, fd&c blue #1, fd&c red #3 and fd&c yellow #6.

Does Stacker2 work?

There’s no scientific research backing the effectiveness of Stacker2. We found studies linking green tea and caffeine to weight-loss, but nothing specific to this formula.

You may want to take a long look at Stacker2 and replace it with a supplement like Leptigen, which contains ingredients clinically proven to work.

How much does Stacker2 cost?

Stacker2 costs $19.99 on the official website.

How should I take Stacker2?

You should take one Stacker2 capsule, three times per day. Each bottle contains 100 capsules or about a 30-day supply. The company recommends not exceeding three pills per day.

Can I take Stacker2 if I have a health condition?

Women who are pregnant or nursing, those with health conditions, anyone taking prescription medications of any kind or under 18 years of age should consult with a healthcare professional prior to using weight-loss supplements, including Stacker2.

What do users like about Stacker2?

Some users like that Stacker2 is a small capsule, making it easy to take and the affordability of the supplement.

What do users NOT like about Stacker2?

We found that some users didn’t like the side effects from Stacker2 and that the product didn’t help dieters lose weight.

How do I contact the Stacker2 customer service department?

You can contact the Stacker2 customer service department by emailing support@stacker2.com, mailing correspondence to NVE Pharmaceuticals 15 Whitehall Rd. Andover, NJ 07821 or by calling a representative at 1-973-786-7868.

If I take more Stacker2, will I improve results?

No, you will not improve results if you take more Stacker2.

How much caffeine is in Stacker2?

Each serving of Stacker2, one capsule, contains 200mg of caffeine.

Does Stacker2 come with a guarantee?

There’s no mention of a guarantee with Stacker2.

Do you know of any special deals or discounts on Stacker2?

There are special deals and discounts on Stacker2. You will receive free shipping on all orders of $50 or more. However, the last several months have been a whirlwind with our readers taking advantage of Leptigen’s Special Trial Offer, which is simply the cost of shipping and handling. Click here to give it a try.

Stacker 2 Side Effects:

Stacker 2 is a supplement that contains ingredients such as green tea, caffeine, and white willow bark to help boost metabolism and boost weight-loss. We know that they are uncommon, but we went out and found comments from users who experienced side effects.


“The third day I was waking up with mild headaches.”    Bailey


“Gave me a headache and sometimes nausea.”    Gregory


“I noticed it also made me jittery and sometimes gave me a headache.”    Thurston


“When I bought this product I was expecting to get a boost of energy instead I got headaches.”    Fredrick


“Makes me jittery, and actually got sick to my stomach.”    Dave


“I started getting weird pains in what seemed like my liver.”    Bryan


“I just started taking this product last week and now I’m having problems with cramps in my legs, my whole body is jittering, and I can’t sleep.”    Adam


“This product made me really sick!”    Lucy


“Made me feel like my heart would explode.”    Rachael


“I go to sleep and get around 7 hours of sleep (just right for me). I was barely able to wake up the last 2 or 3 mornings without feeling like I had no sleep at all.”    Stephanie


We want you to have the best experience while losing weight and we don’t want you to suffer from harmful side effects, that is why we suggest you try Leptigen. It is the top fat burner we’ve seen in 2016. The ingredients have been clinically tested to and shown to help you lose weight.

Click here to check it out!

We really researched Stacker 2 ingredients to help you fully understand the specifics.

Yerba Mate (leaves)

Sometimes called green mate or hervea, yerba mate is a plant that’s often used to make beverages. It’s quite popular in certain parts of South America. It’s also used in various energy drinks sold in the US. It provides some caffeine, as well as vitamins and antioxidants.

What is it Supposed to Do?

Well, yerba mate is found in a number of weight-loss products. It’s typically claimed to boost energy levels, stimulate metabolism, enhance focus and elevate mood. These benefits are all linked to the caffeine in this herb.

Clinical Research

According to the National Institutes of Health, yerba mate has shown some promise in mice. One study revealed, “Yerba Mate has the ability to decrease the differentiation of pre-adipocytes and to reduce the accumulation of lipids in adipocytes, both of which contribute to a lower growth rate of adipose tissue, lower body weight gain, and obesity.” Therefore, “Yerba Mate can potentially be used to treat obesity and diabetes.”

Clinical studies are certainly an important factor when it comes to finding a diet supplement. You might want to check out a product like Leptigen. It uses key ingredients that have been researched.

Green Tea (leaves)

Herbal teas are commonly consumed around the world. This is especially true in Asia. Green tea is a variety that grows in regions such as China and Japan. It differs from black tea because it’s unfermented.

What is it Supposed to Do?

First off, green tea contains both caffeine and EGCG (epigallocatechin gallate). Therefore it provides a stimulant and polyphenol. Together these components can help boost thermogenesis.

Clinical Research

Some clinical studies have shown the benefits of green tea on weight-loss. One study from the University of Maryland Medical Center says, “Clinical studies suggest that green tea extract may boost metabolism and help burn fat.” In fact, one study revealed, “The combination of green tea and caffeine improved weight-loss and maintenance in people who were overweight and moderately obese.”

Guggulsterone (whole plant)

Also called guggul or devadhupa, guggulsterone is actually made from tree sap. Specifically, it comes from the Commiphora mukul tree, which grows in India. Sometimes this ingredient is used to treat acne blemishes.

What is it Supposed to Do?

Guggulsterone is often claimed to stimulate the thyroid gland. It’s found in many weight-loss supplements. By causing the thyroid to produce more hormones, this can potentially increase the metabolism of fatty tissue.

Clinical Research

Unfortunately studies have shown that guggulsterone does not have much of an impact on weight-loss. For instance, WebMD states, “Research suggests that guggul does not affect body weight in overweight or obese people.” However, this plant extract has been shown to help treat acne breakouts.

Is There Anything Out There That We Think TRULY Works?

There is one diet supplement that stands out. Leptigen, which is made with ingredients that HAVE been clinically tested, is a good choice. All customers can benefit from the Special Trial Offer, currently available. Click here to give it a shot.

35 User Reviews About Stacker 2

Leave comments below
  • 1

    Great energy boost for working out, but a but of jitters and a bit of stomach discomfort but not that bad. Hunger suppression is great. restless sleep though. on and off mild headache. will not burn fat alone but helps increase the intensity of my workouts and kill hunger. i pretty much use it as a pre-workout. i have dropped 40 pounds in 3 months.


  • 2
    Your Name

    Stacker 2 is definitely the cause of my trip to the ER. The pulls are very strong and taking one with a petite build is definitely dangerous. I took one recently and had to go to work feeling like I was having a stroke. Some people can handle stacker 2 and will say it is not the pill sending people to the ER but it is. Some people cant handle it. I recommend taking a third of a pill to start off or just dont use it at all.


  • 3

    My daughter drank a can of this she was throwing for at least 5 hours. Did it again months later did it again so.yes it was the stacker 2.’she was fine both.times before she drank.it. Please don’t use this stuff these drinks are dangerous.


  • 4
    Your Name

    I just need to know if it can make your skin itch? I started taking it about a month ago and then the itching started. It was my husband that figured out the itching started about the same time as when I started Stackers 2. I also take a thyroid pill but have for years. Could they conflict with one another?


    Jessica (Editor)

    Hello. All users are different and can experience different results; please make sure to consult with your physician before continuing this product to make sure its safe and effective for you to use.


  • 5

    I took one pill at 6 am. I feel jittery and my heart is racing. It’s almost 2 pm now and my pulse is 130. I don’t like this pill.



    I went to the emergency room almost unconscious and committing for hours. I am lucky to be alive


  • 6

    I was size 20 and 240 pounds before I start on stacker 2 ,when I took stacker 2 I love it ,it boost my energy to go the whole day ,it help me not to want food all the time but most of all it drop me down to a size 14 and 195 pounds,I stop using it when me and my boyfriend tried for a baby and we did have one 2 months ago I gain up to 249 and back up to size 18 now I just start on stacker 2 today had to loose all that weight before work and …..yes ….it may not work for everyone but it definitely work for me !!


  • 7
    carol king

    stacker 2 was horrible for me I have been sick to Stomach throwing up for 6 hours now extremely jittery chills not safe very scary feeling



    These folks with their back killing them, throwing up for days at a time, having to go to the ER for their legs being ‘jelly’…..I’m no doctor, but I would bet that it’s not the ‘stackers’ that are making your THAT ill. Find out what is really going on before you blame them. Seems to me, you didn’t wash your hands well after going out and you caught a stomach bug or the flu. Some major dramatics going on. It’s probably safe to say, those are the ones who are going to sue the company for millions when you probably just had too much dairy.



    I can’t speak for the pills but the 8.3 oz stacker energy drinks (gyrating grape)- those should be labeled as colon cleansers! Disgusting stuff. The 3 separate occasions i’ve drank one i’ve been in the bathroom the rest of the day! I’m now lodging a complaint with the FDA for this garbage for that reason and the fact that they don’t disclose the caffeine content.


  • 8

    I tried the 4 pack pills, could not tell I even had taken one at all… I want my 5 hour energy drinks back… NOW!!!
    These things DO NOT WORK!!!!


  • 9

    Tell us your thoughts about Stacker 2. i have been taking it for about 4 days. just one in the morning. yes it gives me tons of energy, but remindes me of speed. or what i think it would be like. but, its doing what i wanted which is keeping me from getting hungry. it cheeper than red bull, but will it be addictive well see. this product i know will not burn fat unless you use it with excercis. but im very lean as it is and walk a lot each day.


  • 10
    Ylolaour Name

    i started using rhis product two weeks ago it just made me lose the craving not the fat


  • 11
    Your Nalol sme

    its great i just started taking the stacker 2 and it gave me energy and less cravings. I recommend to those who are trying to lose the late eating crash


  • 12
    Your Nadonnarachieleme

    Gave me a headache made me nauseated


  • 13

    I took stacker 2 many years ago. I believe it was in the 80’s and it gave me an incredible amount of energy and it was like it melted the fat away without diet and exercise. I swear by stackers 2. I couldn’t believe how it melted the fat away without even cutting out any of the food I normally eat and I had lost 90 pounds but once you stop with any diet pill you gain back the weight you lost and then some. Don’t get me wrong it did work for me but to keep the weight off you must continue to take the diet pill no matter what one it is that you’re taking.


    Your Name

    Ya but you don’t always wana depend on a pill to make u loose weight , once u stop taking the pill u could start exercising more often or even on a simple duet such as fruits and veggies and if u love meat just watch how much your eating plus breads or anything along that line can lead to weight gain….?


  • 14
    David Baker

    I used the original stacker 2 when it had the ephedrine and it was awesome !! lost 80+ lbs but when they changed the formula it just did not work for me anymore. now years later I have regained the weight and am still searching for something that works !!


  • 15

    Today is my first day on stacker, iv took 1 pill after bereakfast and ran on treadmill for like 15 min, and I feel like iv got plenty of boost to go to work and make it happen!!! I’ll post back in few days for furtthur updates…?


  • 16

    Stacker 2 may not burn fat alone but it definitely gives your workout a boost!


  • 17

    I took two stacker 2 pills and they gave me energy but I got jittery and nauseated and I couldn’t sleep that night. I tried them again next day but only took about a 1/3 of a pill and I got better results.


  • 18

    Can it make hair thin


    Stephen (Editor)

    Hi. Laurie. It is quite possible, though to be sure please consult with your doctor.


  • 19
    Your Name

    I just got some to day I’m gonna try them be cause I hear their its good energy boost. So hope it works for me


  • 20

    stacker works great for energy made it through a long day at work which usually drags on and on heart rate does go up a little but not bad as for the weight loss part not sure just started taking them today i took 1 after breakfest and 1 after lunch and no problems it delivers a big boost in energy


  • 21
    shawn williams

    stacker work for me i have energy all day long i try others diet pills but i didnt have energy….for me i have to stick with stackers.



    I agree! I only take one pill in am and that’s it. It gives me energy to work out and no side effects!


  • 22

    I use stacker 2 everyday. I only take 1/3rd of a cap,you dont need to take a lot to make it work.Small amounts will give you a boost without making you feel sick, your weight loss will come from diet and exercise not from pills.


  • 23
    donna davis

    i been takin stackers2 for 1 week i felt like my heart was gonna bust my back hurts my stomac hurts my leggs feels like there jelly im so exculsted all i wanta do is sleep im soo sick i wanna die that i cant stand the pain im going to the er tommorow and get help i may end up sueing for this pain n suffring i have kids that i need to focuse on i trusted this diet pill all it did was put me in pain ill never take3 this trash agean thanks for this sevier pain i hope they take this junk off marketmarche



    Not for you you may have allergic reaction works great for me


    Your Name

    Tou should not take three at once and you can but not sue,you should know he risk and need to realize being smart and not overdosing is wise!


    Your Name

    I’m sorry, but i guarantee you……you being that sick had nothing to do with Stackers.


  • 24
    joseph hyde

    well stacker made me feel really bad and i got sick and my heart had pain in it so i dont know whats going on but i dont like it im not buy stacker no more bye


  • 25
    cindy shippy

    i thought i was going to die after taking stacker 3. they shouldnt be sold. my whole boby inside and out shook .


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