XXL Nutrition Fat Killer Review: 5 Things You Must Know About This Fat Burner

XXL Nutrition Fat Killer Review

Here’s our XXL Fat Killer Review.

Losing weight is an extremely difficult process, so people naturally look for ways to make things easier and faster.

Generally speaking, fat burners do work, but there’s a mountain of junk out there that uses ineffective ingredients. These fat burners, which make up 90% of the market, not only leave a hole in your wallet but also sometimes cause side effects.

A good fat burner needs to:

  • Be 100% natural
  • Have a safe and effective dose of stimulants to boost your metabolism
  • Increase your energy levels
  • Reduce your appetite and cravings
  • Be made by a reputable manufacturer
  • Have excellent reviews online

Most fat burners rely on caffeine to amp you up, but that doesn’t bring many benefits long term – it only leaves you feeling jittery.

The best fat burners use a combination of the right ingredients, in the right doses, to achieve the maximum natural effect on your appetite, stored body fat, and metabolic speed.

About XXL Nutrition Fat Killer – What are its Claimed Benefits?

Back to Fat Killer by XXL Nutrition. How does it work and does it even work?

The successor of XXL Nutrition’s popular Fat Attack supplement, Fat Killer comes in bottles of 120 capsules and promises to help accelerate your dieting and training by helping you to burn more fat as energy throughout the day.

It features ingredients such as L-Carnitine, kaempferol, and caffeine, some of which are tried and tested fat burners and some which don’t have much research behind them. More on this below.

According to XXL Nutrition, Fat Killer is formulated by professionals, so you can rest assured you’re getting the benefits without the risk of side effects. Let’s see how accurate these claims are – and if it’s worth the €34.95 it costs!

What do we recommend?

>Top 5 Fat Burners of This Year<

1. How to Use XXL Nutrition Fat Killer

First time Fat Killer user? Start with 1 capsule with your meal.

See how you respond to it. If you respond well, then you can take the full dose of Fat Killer which is 2 capsules with a meal per day.

Don’t go above 2 capsules within 24 hours! The caffeine dose if pretty high and can cause you issues if you aren’t careful.

Is this a good way to take a fat burner?

Taking only 1 serving of a fat burner per day is a convenient and simple thing. You pop your pills and let the ingredients to the work – sound good right?

Well, there’s a reason why the most effective fat burners use 3 or even 4 servings per day. This keeps your body topped up with fat burning nutrients throughout the whole day.

Related: Flat Tummy Apple Cider Vinegar Gummies Review

What can one dose do? It can spike your metabolism and energy for a couple of hours and then you’re back to baseline. Obviously, we’ll want to keep our body in a constant state of elevated energy expenditure to really see the benefits.

2. The Ingredients

Here we come to the most important part. If the ingredients are good, it can help your body burn more fat and reduce your feelings of hunger, while also increasing your mental energy so you’re more likely to stick to your goals.

To start on a positive note, XXL Fat Killer uses some pretty decent ingredients – there’s caffeine, green tea extract, and chromium. While caffeine stimulates your central nervous system, green tea extract works to rev up the thermogenesis, a process where your body burns off its own fat to produce extra heat.

But here’s the issue: all but 2 ingredients of XXL Fat Killer are in a proprietary blend. What does this mean?

It means, we can’t see the ingredient doses that are in the blend. We only see their combined dosage, which tells us very little about the safety and effectiveness of these ingredients.

See for yourself:

Ingredient Breakdown

  • Caffeine (256mg) – I don’t think there’s anyone who doesn’t know what caffeine is. If you know that person, let me know! Anyways, caffeine is an integral ingredient in fat burners because it helps you lose weight from multiple angles; one, it revs up your metabolism to burn calories more efficiently. Two, it curbs hunger a bit (not the most effective natural appetite suppressant out there though!). Third, it increases energy so you have more motivation to train and stick to a healthy diet.
  • Green Tea (UNKNOWN DOSE) – Green tea is one of the most used ingredients in fat burners, and for good reason. It works as a thermogenic, which means it raises your core temperature so your body has to adjust by burning more calories. Alongside that, green tea provides some healthful antioxidants called catechins. However, the dosage of green tea’s active ingredients are unknown here, so we can’t tell how effective it will be.
  • Acetyl L Carnitine (UNKNOWN DOSE) – Another commonly used fat burner ingredient, though this one hasn’t been proven to work for weight loss. Also, the “acetyl” part allows it to cross your blood-brain barrier, which makes this ingredient a better choice for a nootropic than a fat burner!
  • Chromium (12mcg) – This is a good choice. Chromium lowers your blood sugar levels, making you feel less groggy after eating a meal. Stabilizing your blood sugar also has the added benefit of lower insulin levels, which will help reduce the amount of fat that you gain from eating food.
  • Kaempferol (UNKNOWN DOSE) – Kaempferol is a natural compound found in cruciferous vegetables like kale. Although understudied, early evidence shows promising results in terms of weight loss. Again, the dosage in XXL Fat Killer is unknown – it could be as low as 1mg per serving and completely ineffective, without us being able to tell.
  • Coleus Forskholii (UNKNOWN DOSE) – This is a plant most famous for its compound Forskolin, which is shown to affect a molecule in your body called cAMP which is thought to affect fat breakdown. The issue is, Forskolin’s effects on cAMP are so weak that it doesn’t lead to any long-term benefits.
  • L-Tyrosine (UNKNOWN DOSE) – Tyrosine helps your brain make more dopamine, which your brain uses to focus and motivate you to stay disciplined with your goals. It’s a really good ingredient, which is why it’s even more annoying that we can’t see its dose!

Our Thoughts on the Ingredient Profile

The ingredients themselves are decent. Tyrosine, Green Tea, Caffeine, and Chromium can all contribute to you getting leaner in one way or another.

However, apart from the lack of transparency in terms of dosages, XXL Fat Killer is also missing some important ingredients that we often see in the top-rated fat burners – such as Glucomannan (appetite suppressant) and Cayenne Seed Extract (thermogenic).

Editor’s Pick:

The Five of the Best Fat Burners of 2021

3. Customer Reviews

We’ve scoured the internet for Fat Killer testimonials with very little luck.

Apart from their own official XXL Nutrition website, you won’t find many reviews of Fat Killer online. This appears to be more of a micro-niche fat burner catering to very small audience of people – primarily those from the Netherlands, UK, and Germany.

4. Does XXL Nutrition Fat Killer Have Side Effects?

Caffeine dosage in Fat Killer is within the safe limits but you should thread carefully if you don’t tolerate stimulants.

Too much caffeine can cause:

  • Jitters
  • Anxiety
  • Insomnia
  • Heart palpitations

As for the other ingredients in Fat Killer, it’s hard to say if they will cause side effects since we don’t know their doses.

With that being said; the ingredients themselves are quite common in fat burners. Unless they’re dosed extremely high, they shouldn’t really give you side effects. Of course, if you have any concerns, it’s best to talk to your local health authority before buying a supplement like this one!

5. The Bottom Line

XXL Fat Killer is a fat burner with some good ingredients, it’s a shame they didn’t show us the doses of most of them.

We only know there’s 256mg of caffeine and 12mcg of chromium per serving – as for the rest, you’re left guessing!

Caffeine will definitely give you an energy kick and may help to reduce your cravings.

However, it would be a far better fat burner if it removed some of the ineffective ingredients (like Carnitine), added more proven ones, and showed us the doses clearly on the label.

It’s relatively affordable at €35 per bottle (60 servings) though, so if you don’t mind the proprietary blend and not knowing exactly how much of what you’re getting, then this can be a good option for you.


  • 120 capsules per bottle yielding 60 servings
  • Green tea extract, caffeine, and chromium are all excellent fat loss ingredients
  • L-Tyrosine is added to help improve your focus and mental well-being


  • Unknown ingredient doses
  • A few ineffective ingredients, such as Forskolin
  • Missing an appetite suppressant and a few other essentials
  • We haven’t found it to be effective for weight loss, although the caffeine did give us good amount of energy

-Click for Top 5 Fat Burners of This Year-

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