You’ve hit a wall and need help to lose weight?
Although there’s no magic diet plan or pill for those expecting to shred fat while sitting on a couch and snacking, some pills can effectively support your workout and dieting efforts and help you achieve faster weight loss results.
This review reveals whether Stacker 2 is “the world’s strongest fat burner” as marketed.
Let’s see what this product claims to do and whether it melts the fat away as it promises.
What Is Stacker 2 Fat Burner?
Stacker 2 is advertised as “the world’s strongest fat burner” claimed to help users boost energy, curb cravings, burn fat, and lose weight quickly in combination with a balanced diet and exercise.
This product was made in the USA by a New Jersey company NVE Pharmaceuticals more than two decades ago.
It’s been wildly popular probably because it’s been endorsed by celebrities, ubiquitously advertised on social media, in magazines, and elsewhere.
The original product formula with ephedra has been changed over time because it contained this harmful, banned substance.
Although Stacker 2 is now ephedra-free, made with herbal ingredients, easy to get, and really affordable, it still doesn’t mean it’s completely safe.
Let’s take a closer look at the key active ingredients of this supplement, their good and bad sides, and whether they can verify the manufacturer’s claims with their effects.
What Are the Ingredients in Stacker 2?
The main active ingredients in Stacker 2 are the following:
Caffeine Anhydrous (200mg)
This potent stimulant mimics neurotransmitter adenosine to help improve mental alertness and exercise performance. It may provide an energy boost, reduce hunger and fatigue, and trigger thermogenesis to burn fat and stimulate weight loss.   
Similar product: PhenGold (Review)
Proprietary Blend (267mg)
Yerba Mate (Leaves)
Apart from being rich in vitamins, minerals, antioxidants, and amino acids, Yerba Mate is another stimulant containing caffeine believed to improve mood and satiety or reduce tiredness. 
You may also like: Lean-XT (Review)
Green Tea Leaves
Green tea might be slightly effective in weight loss supplements, but there’s conflicting evidence about its benefits.
It’s abundant in antioxidants and other important nutrients but also contains caffeine said to improve mental alertness and trigger thermogenesis. 
My two cents:
They tried to replace ephedra with crazy amounts of caffeine in hidden doses.
Also read: Liquid Burn (Review)
Although Guggulsterone contains plant steroids that might regulate your triglycerides, cholesterol, and appetite, most research can’t validate its effectiveness in weight loss. 
Plus, it can mess us with your hormones and cause blood clotting disorders. 
Cassia Mimosoides Extract
Cassia Mimosoides Extract might support weight loss in some people by preventing the absorption of dietary fat in the intestines and promoting their excretion.
Yet, there isn’t enough reliable evidence to confirm its safety and effectiveness, especially when it’s dose is hidden behind proprietary blends. 
White Willow Bark
White willow bark has natural anti-inflammatory, antioxidant, and analgesic effects like Aspirin.
Although its tannins and flavonoids may benefit your health, white willow bark is a blood thinner that might damage your liver and brain. Plus, no human studies can directly prove its benefits. 
How Does It Work?
This supposedly powerful ephedra-free formula is claimed to suppress your appetite, raise your metabolic rate, increase your energy levels, and stamina to enable you to train harder, burn excess body fat and lose weight fast.
However, there isn’t sufficient scientific research to back up the claims on the effectiveness of this formula.
Even the manufacturer says that this product is intended to be combined with a restricted diet, regular workouts, and other supplements to help people see any results, i.e. reach their fitness and weight loss goals more effectively and quickly.
- The brand has been present on the market for a few decades
- Updated ephedra-free formula
- Some users have said it can increase energy
- It might help control your appetite
- Formula not studied enough to verify the manufacturer’s claims
- Contains a proprietary blend with non-transparent doses of ingredients
- Too high in caffeine
- High chance of experiencing adverse reactions (as many people have complained)
- Contains some controversial, artificial inactive ingredients
Other fat burners worth checking out: Animal Cuts (Review)
What Are the Side Effects of Stacker 2?
These are the side effects of Stacker 2, according to users’ experiences:
- Severe headaches
- Upset stomach
- Short breath
- Rapid heartbeat
- Increased blood pressure
- Insomnia, etc.
Most side effects occur due to the high caffeine amount, so be extra cautious if you’re oversensitive to it or consuming it from other sources as it may cause serious adverse effects.    If that's the case, we highly advise you to opt for a caffeine-free weight loss product instead.
“Caffeine in powder or liquid form can provide toxic levels of caffeine, the U.S. Food and Drug Administration has cautioned. Just one teaspoon of powdered caffeine is equivalent to about 28 cups of coffee. Such high levels of caffeine can cause serious health problems and possibly death.” - Mayo Clinic
These capsules may interact with alcohol and some medications, so you should avoid alcohol and seek medical advice first if you’re using any other pills. Also, minors, pregnant, or nursing women shouldn’t use this product, but you can try one of the proven fat burners for women.
Other products we've reviewed: Ripped Fast (Review)
Besides expert opinions and numerous studies, we’ve gathered customer reviews from those who really use(d) this product.
As expected, individual results vary.
Interestingly, most positive reviews praise the supplement for the energy increase it can give, while only a few users seem to be satisfied with its weight loss assistance.
No wonder those who have rated this supplement with 5 stars compare it to “reasonably priced meth” and “crack in a bottle”.
Here are some typical experiences people have shared online:
“I haven't lost any weight using these as I tend to use them to keep me awake through the day, so I don't take them consistently. However, as a pick-me-up, they work great. Just don't take them on an empty stomach.”
“Been using this product for years. I only take one a day for energy that last all day! Can’t do the stacker 3 or xlt they make me shaky and give me the jitters but Stacker 2’s are perfect.” - Pamela
“It really gives me energy to get through my day.” - James
“Definitely helps curb the appetite and increases energy.” - Tia
“I used this years ago and lost a lot of weight this one the newer version I haven’t lost a lbs.” - Katelyn
“Helps with energy not weight loss.” - Oya
Other fat burners we've reviewed: Clean Burn (Review)
Where Can You Buy Stacker 2?
You can buy Stacker 2 from the company’s official website or other retailers. One bottle of Stacker 2 contains 100 pills, which is sufficient for about a month.
How Should You Take Stacker 2 Weight Loss Supplement?
You should take one Stacker 2 capsule three times a day after meals. The manufacturer suggests not taking more than three capsules per day.
Do Stacker 2 Weight Loss Pills Provide Energy Boost?
Stacker 2 weight loss pills are claimed to provide an energy boost.
Other weight loss product that provides great energy boost: B4 Thermogenic (Review)
How Much Caffeine Is in a Stacker 2 Pill?
There is a great deal of caffeine in a Stacker 2 pill per serving - 200mg from Caffeine Anhydrous, plus an unknown amount from the other ingredients like Yerba Mate or Green Tea hidden within the proprietary blend.
Are Stacker 2 Diet Pills With Ephedra?
How Long Does Stacker 2 Stay in Your System?
Stacker 2 may stay in your system for a couple of days.
Is Stacker 2 Fat Burner Worth It?
Ephedra-free Stacker 2 is definitely not the world’s strongest fat burner as advertised.
Would I still give it the thumbs up? I’m skeptical that it’s worth a try.
No substantial scientific evidence supports the manufacturer’s claims. Besides, many users haven’t seen any results and have experienced unpleasant side effects after taking this product.
Why take a health risk when there are better and safer weight loss products tried, tested, and clinically-proven to work?!
When it comes to fat burner recommendation, I always go back to PhenQ - the one with scientifically backed potent thermogenic ingredients without the proprietary blend.
The doses are transparent and hundreds of thousands of people swear by it.