Decathlon Muscle Gainer Whey and Oats Review

A picture of Best Mass Gainer UK founder, personal trainer Andy Williams
Written By
Andy Williams
Last Updated on

When it comes to building serious muscle mass, finding the right gainer can be quite a challenge. That's where I come in! I recently got my hands on Decathlon's Muscle Gainer Whey & Oat Chocolate and decided to put it through its paces. 

In this Decathlon mass gainer review, I'll be sharing my experience with Decathlon's Muscle Gainer to give you the lowdown on its taste, mixability, and effectiveness.

I also tried and tested 60+ other weight gainers recently, so it’s going to be interesting to see how Decathlon Whey and Oats compares to the rest of the supplements on the market.

ideal for weight gain
Decathlon Muscle Gainer Whey and Oats
A bag of Decathlon Muscle Gainer Whey and Oats ready for review
Taste: 8.5/10
Mixability: 9/10
Ingredient Quality: 9/10
Mass-Building Potential: 8.7/10
Overall Rating: 8.8/10
  • Contains 375 muscle-building calories per serving. Ideal for bulking up.
  • One of the few gainers to use high-quality grass-fed whey protein.
  • Boasts an ideal 36g protein dose per 100g serving.
  • Keeps your muscles full and recovered with 45g of quality carbs—no maltodextrin.
  • Great taste (especially for a mass gainer) and easy to mix with both water and milk.
  • Good value compared to more popular brands.
  • Some extreme hardgainers may prefer a higher-calorie shake
  • May have limited availability at times.

Decathlon Muscle Gainer Nutrition Facts

The Decathlon Muscle Gainer nutrition facts

Alright, let's talk about the nutrition facts of Decathlon Muscle Gainer. I've gathered the key nutritional information so you can quickly understand what this supplement has to offer.

  • Calories: Each serving provides roughly 389 kcal, which is a solid addition to your daily caloric intake if you're aiming to bulk up and add size to your frame.
  • Carbohydrates: Decathlon Muscle Gainer contains a healthy source of carbs (oats) and is a maltodextrin free mass gainer, making it ideal for those looking to gain weight without storing much fat.
  • Protein: This gainer offers high-quality protein—premium grass-fed whey—with each serving containing a substantial 36g dose. 
  • Fats: This Decathlon weight gainer has around 5g of fat, which is fairly typical for this kind of supplement, which is by nature protein and carb-heavy.

Decathlon Muscle Gainer Ingredients

Grass-Fed Whey Protein

The key ingredients in this Decathlon Mass Gainer

Since grass-fed whey comes from cows that have been raised on natural, pesticide-free pastures, we get a purer, more nutrient-dense protein source that aids muscle growth and recovery without causing unpleasant side effects.

Decathlon mass gainer contains high-quality, grass-fed whey protein. When it comes to building muscle mass, providing the best protein possible is crucial because muscles thrive on having a full spectrum of amino acids at their disposal.

Quality Carbs From Oats

To my delight, the team at Decathlon have chosen to use oats as the primary carbohydrate source in their Decathlon weight gainer. This is great because oats are not only a rich source of complex carbs, but they also provide essential vitamins, minerals, and fibre to support overall health. 

Specifically for bodybuilding, the carbohydrates from oats help replenish muscle glycogen stores after intense workouts, promoting muscle repair, growth, and fullness.

And for bulking, these quality carbs will help to trigger weight gain while minimising fat storage. That’s right; there’s no maltodextrin in this mass gainer.

Natural Flavouring

I believe in keeping things natural, and so does Decathlon. Their Domyos mass gainer is flavourful yet guilt-free to drink. They use natural flavouring in their Decathlon Muscle Gainer Whey and Oats gainer, providing a delicious taste without relying on artificial additives or excessive sugar.

No Fillers or Creatine

Side view of the Decathlon Mass Gainer

It's essential to me that any mass gainer I recommend provides you with everything you need for muscle growth without unnecessary ingredients. In other words, no hidden nasties! 

That's why you won't find any fillers or creatine in Decathlon Muscle Gainer Whey and Oats. Just good ol’ protein and carbs. No need to be flashy when it comes to gaining muscle. Let the quality ingredients do the work, not your marketing!

The team at Decathlon is committed to providing a clean, effective formula focused on delivering the nutrients needed to support muscle gain. 

In this sense, the product is similar to the Healthspan Elite All Blacks Mass Gain Protein Blend, which is another quality high-calorie shake.

When Should You Take This Decathlon Mass Gainer?

The scoop from Decathlon Muscle Gainer

In this section of my Decathlon mass gainer review, I'll discuss the ideal timings for this weight gainer so you can maximise your muscle growth and recovery. 

Obviously, you don’t have to drink this gainer on every occasion during the day (that would likely result in an excessive calorie intake).

Post-workout is the obvious time to drink this gainer, but you can also drink it as a breakfast shake, for example.

As for how many times to take Decathlon Whey and Oats, that really comes down to how many calories you personally need to consume, which is mostly based on your body weight and activity level.

At Breakfast Time

A great time to consume this mass gainer is at breakfast. Since your body has been fasting overnight, it's smart to provide it with essential nutrients and a good amount of calories to start the day in order to support your energy levels and prevent muscle breakdown.

Before Training

Taking this mass gainer prior to training will fuel your workouts, providing you with enough energy to perform more intense exercises (which, in turn, can lead to more muscle growth). 


After an intense workout session, your muscles are in need of nutrients to help repair and grow. Consuming Decathlon Mass Gainer post-workout can help replenish those depleted nutrients and maximise recovery. 

The proteins and carbohydrates present in the mass gainer can boost glycogen synthesis and trigger muscle protein synthesis, thus promoting muscle growth.

A bag of Decathlon Muscle Gainer Whey and Oats ready for review

Before Bed

Another excellent time for having this mass gainer is right before bedtime because our bodies go through a lot of repairing and rebuilding during sleep. 

Therefore, consuming a mass gainer before bed ensures that your muscles receive a steady supply of nutrients—especially amino acids—throughout the night to support hypertrophy and reduce overnight muscle breakdown.

To see the lowdown on another good gainer, you might want to check out my review of PE Nutrition Performance Gainer.

How To Take Decathlon's Weight Gainer

An overhead view of Decathlon Weight Gainer

Here's a quick guide on how to properly take Decathlon's Muscle Gainer, so you can get the most out of it.

First off, it's important to measure the right amount of powder for each serving. For this particular weight gainer, I recommend using 100 grams of the product. Grab your trusty shaker or blender and pour the powder in—it'll help you get a smooth and evenly mixed drink!

Next, let's talk about liquids. You've got some choices here, but I suggest using water or milk—or even a combination of both if that tickles your fancy. You'll need about 250 to 300 millilitres to mix with the 100 grams of powder. Give it a good shake or blend to make sure everything is nicely combined, and you're good to go!

Decathlon Muscle Gainer Flavours And Mixability

A bag of chocolate Decathlon Muscle Gainer Whey and Oats

Decathlon Muscle Gainer is available in a delicious chocolate flavour that tastes more like a milkshake than a typical mass gainer. And it’s not just me who thinks that!

Before launch, the chocolate flavour of Decathlon’s Muscle Gainer was tested and approved by 92% of the product testers, with 86% feeling that the product's composition came from natural sources.

Also, 98% said the recipe provided effective nutritional values. 

Now, when it comes to mixing Decathlon Muscle Gainer Whey and Oats, I’m happy to report that the powder and liquid combine effortlessly to form a delicious mass-gaining milkshake. 

Unlike some other gainers that may clump or become too thick when mixed, Decathlon’s Muscle Gainer maintains a smooth consistency. Plus, it's suitable for blending into water or milk, which gives you the flexibility to enjoy the drink however you prefer.

Who Should Avoid Decathlon Muscle Gainer Whey And Oats?

In my experience, there are certain groups of people who should avoid using Decathlon Muscle Gainer Whey and Oats. While it's a great product for many, it might not be suitable for everyone.

The supplement facts for Decathlon weight gainer

Firstly, if you are aiming to lose weight or simply maintain your current body weight, this product might not be the best choice. Since Decathlon Muscle Gainer is designed to help you gain weight and muscle mass, it's not really suitable for those looking to shed a few pounds or stay at their current weight.

Another important thing to consider is that Decathlon Muscle Gainer has 389 kcal per shake, which is a decent amount of calories for those looking to gain weight. However, if you’re searching for a really high-calorie gainer, there might be other options out there with more carbs and protein that better meet your needs.

Just remember, though, that more calories doesn’t always mean more gains. Past a certain point, those excess calories will either just be burnt off or stored as fat, depending on your activity level.

So, while Decathlon Muscle Gainer Whey and Oats can be an excellent choice for many, some people might need to pass on this particular product and explore other options when it comes to muscle and weight gain.

I’d say that this Decathlon gainer is better than Hectic Sports Mass Gainer Whey Protein because it has way less fat and doesn’t have any added creatine.

Is Decathlon Muscle Gainer Whey And Oats Worth A Try?

Closeup of Decathlon Muscle Gainer Whey and Oats

In this Decathlon weight gainer review, I've been looking into Decathlon's Muscle Gainer Whey and Oats, and it seems like a promising option for those looking to gain muscle or maintain their muscle mass. 

Firstly, the product has received good reviews from users. At the time of writing, the chocolate-flavoured Muscle Gainer has a 4.3/5 rating based on over 100 reviews, while the vanilla version scored an overall 4.1/5 among product testers. 

In fact, 80% of the testers gave the vanilla gainer a score of 4/5 or 5/5. This indicates that a majority of users find it effective and feel satisfied with their purchase.

The mixture of whey and oats provides a high-quality source of protein and carbs for muscle repair and growth, rather than fat storage. This makes it a healthier and more effective option compared to some other gainers on the market.

In summary, Decathlon's Muscle Gainer Whey & Oats seems to be well-received by users and provides a healthy, effective, and convenient option for those wanting to build or maintain their muscle mass. If you're considering trying a muscle gainer, it's definitely worth taking a closer look at this one.

Hopefully, you found my Decathlon Muscle Gainer review helpful and have great success on your muscle-building journey!

The #1 UK Mass Gainer
Crazy Nutrition Mass Gainer
Two bags of Crazy Nutrition Mass Gainer positioned side by side
  • Contains 488 bulking calories from 100% clean sources
  • Packed with a proven 40g protein blend for quick muscle repair and growth
  • Provokes noticable weight gain with 55g of complex carbs from oats
  • Tastes amazing (to my surprise!) and mixes easily
  • Offered at the absolute lowest UK price during April
A picture of Best Mass Gainer UK founder, personal trainer Andy Williams
Andy Williams
Andy Williams is a UK-based personal trainer and bodybuilder who coaches gym-goers of all levels using proven evidence-based techniques in strength training, nutrition, and supplementation. He’s tested over 70 different mass gainers for their ingredient quality and muscle-building effectiveness and regularly shares his findings in his mass gainer reviews.
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