Serious Mass Vs Pro Gainer: Which is Better? (Pros and Cons)

Optimum Nutrition Serious Mass is the better choice if you are looking for more calories and carbohydrates. It is also an ideal choice if you are looking for creatine monohydrate in your weight gain shake.

Optimum Nutrition Pro Gainer is better for you if you are a casual gainer who just needs decent amounts of calories. It is also a suitable choice if you prefer more protein and less sugar in your mass gainer.

In this post, I will be reviewing 2 Optimum Nutrition weight gain shakes: Serious Mass and Pro Gainer. I evaluated these mass gainers based on:

  • Calorie content
  • Protein 
  • Flavor
  • Pricing
  • Added nutrients

After reading this review from start to finish, you will have an easier time picking which mass gainer will work best for your bulking diet.

I will cover the most deciding factors in-depth. But before we dive in, here’s a quick snapshot of what I found:

Optimum Nutrition Serious Mass

Overall rating

4.6 out of 5.0 stars

Calorie profileProtein contentFlavorPricingExtras
5.0 out of 5.0 stars5.0 out of 5.0 stars4.0 out of 5.0 stars4.0 out of 5.0 stars5.0 out of 5.0 stars

Optimum Nutrition Pro Gainer

Overall rating

4.2 out of 5.0 stars

Calorie profileProtein contentFlavorPricingExtras
3.0 out of 5.0 stars5.0 out of 5.0 stars4.0 out of 5.0 stars5.0 out of 5.0 stars4.0 out of 5.0 stars

Optimum Nutrition Serious Mass is better for you if:Optimum Nutrition Pro Gainer is better for you if:
– You want more calories and carbs in your shake– You need a little bit more protein in your shake
– You are looking to boost muscle performance– You are looking for casual muscle gains
– You are looking for a low-sugar weight gain shake

Serious Mass vs Pro Gainer: Quick Comparison

Serious MassPro Gainer
Which has more calories?✔️
Which has more protein?✔️
Which is better for hard gainers?✔️
Which offers more flavors?✔️
Which has less sugar?✔️
Which one is more affordable?✔️

What do users say about Serious Mass?

“I never thought I would gain weight in quick time. In 4 weeks I almost gained 9 pounds. I am buying this again for few more pounds gain.
Although the strawberry flavor is not the best one but better than the rest I guess.”

“Optimum Nutrition is one of the only brands I trust when it comes to workout supplements. This is a great product for anyone that struggles to get enough calories in their diet while trying to build mass. 
One bad thing is this product gives me massive amounts of gas. I can use their gold standard protein all day with no intestinal distress but any more than one scoop of this has me pretty gassy later, so I like to go with one scoop of this and a scoop of protein after a workout. 
This is the first time I tried the banana flavor, as I prefer the chocolate flavors, but I wanted to switch it up for once. The banana is good but very sweet, a bit too much for me. 
The macros on this are perfect for me when I add the scoop of protein. I will probably purchase this again but in a different flavor.”

What do users say about Pro Gainer?

“Optimum Nutrition Pro Gainer is one of my favorites. I recommenced getting the vanilla flavor since it tastes good by itself and it is easily mixed with other things to change the flavor. 
I like to add cinnamon to my protein shakes and it taste so good. It is also packed full of vitamins and minerals that your body needs. It is really an all in one bundle with plenty of protein, carbs, fats, vitamins, and minerals.”

“So I’m 25 years old 6 ft and 173 pounds and I have been trying to put on some muscle mass for some time now but I realized I don’t eat enough carbs daily since I’m so busy as a student so I decided to try a gainer, 
Originally I got the traditional gainer with 250 carbs and quickly realized that would just make me overweight since I’m not trying to put on “Serious mass” just another 5-10 pounds of muscle is what I’m looking for.
I’m very picky with protein because some whey proteins give me a nitchy sensation in my throat after taking it and this mix did not give me that feeling so that’s a plus, it also mixed very well compared to Serious Mass, and tastes loads better too!”

Are you ready?Go to Optimum Nutrition Serious MassGo to Optimum Nutrition Pro Gainer


Which One Gives You More Calories?

Calorie-wise, Serious Mass easily leaves Pro Gainer behind. Each serving of Pro Gainer gives you 650 calories, which pales in comparison with Serious Mass’ 1250 calories per serving. 

If you are a hard gainer who has trouble achieving a caloric surplus each day, you are probably better off using Serious Mass instead of Pro Gainer for your bulking needs. 

Serious Mass also gives you a significantly higher amount of carbohydrates (252g per serving) than Pro gainer (85g per serving). For their carbohydrate content, both mass gainers use maltodextrin, which is quickly digested and absorbed by the body.


For ectomorphs who prefer more calories in their weight gainer, Serious Mass is the better choice than Pro Gainer. You get 1250 calories in each shake, which is almost twice what Pro Gainer offers (650 calories per serving).

Which One Gives You More Protein?

Judging by their protein blends, both mass gainers feature fast-, medium-, and slow-digesting protein sources. However, Pro Gainer gives you a bit more protein than Serious Mass. Each serving of Pro Gainer gives you 60g of protein, while Serious Mass comes in close with 50g of protein.

With their well-rounded protein blends, both weight gain shakes can help you build lean muscle tissue and speed up post-exercise muscle recovery.

Serious Mass, however, is enhanced by the addition of 500mg of L-glutamine. This amino acid may help provide added protection against muscle wastage and catabolism.


Both mass gainers give you an impressive blend of protein sources. However, Pro Gainer has a slight edge by providing 60g of protein per serving, compared to Serious Mass that delivers 50g of protein per serving. 

Which One Offers More Nutrition?

Aside from protein, carbs, and calories, it’s always good to check if your mass gainer gives you extra nutrients for staying healthy or boosting your exercise performance.

Both Serious Mass and Pro Gainer contain Medium Chain Triglycerides, a type of fatty acid that is readily utilized by the body as a source of energy – instead of getting stored as unwanted body fat.

Both mass gainer shakes also contain more than 20 vitamins and minerals, which may help fill in any nutritional gaps that might be present in your diet.

Serious Mass looks more tailored for hardcore gainers as it is packed with 3g of creatine monohydrate per serving. Creatine gives your muscles a fuller appearance, and it may also prolong your exercise endurance by buffering the buildup of lactic acid in your muscles.

Serious Mass also contains 250mg of inositol and 5mg of PABA, which may help boost your mood and provide added energy.

Pro Gainer, on the other hand, features digestive enzymes that may help your body absorb, digest, and utilize more nutrients from its formula.


While they both feature vitamins, minerals, and Medium Chain Triglycerides, Serious Mass gets the thumbs up with its 3g of creatine monohydrate content. If you are looking to push your exercise performance to greater heights, Serious Mass looks to be the better choice.

Which One Tastes Better?

As someone who has tasted a wide variety of protein shakes and mass gainers, I can say that it is quite hard to please my taste buds. 

Both mass gainers are made by Optimum Nutrition, so they share similar characteristics in terms of flavor and mixability.

Pro Gainer is made available in Double Chocolate and Vanilla Custard. Serious Mass offers a wider variety of flavor options, such as Strawberry, Creamy Vanilla, Banana, Chocolate, and Chocolate Peanut Butter.

To achieve a smooth and rich consistency, mix your shake with a blender or a shaker bottle. You can also improve the taste of your shake by throwing in a few slices of fruit, a spoonful of oats, or a scoop of ice cream or peanut butter.


Both mass gainers taste decent and mix pretty well with water and milk. While these are not the best-tasting mass gainers out there, you can easily uplift their taste by adding some fruit or peanut butter to your shake.

Which One is More Affordable?

The 12lb bag of Optimum Nutrition Serious Mass is good for 16 servings. Each serving requires 2 heaping scoops and costs roughly the same as a quarter pounder meal.

The 10lb bag of Optimum Nutrition Pro Gainer, on the other hand, is good for 28 servings. Each serving only requires 1 heaping scoop, and costs just a little more than a standard all-beef hotdog sandwich.


When it comes to pricing, Pro Gainer wins hands down. If you are a casual gainer who is on a tight budget, you can’t go wrong by choosing Optimum Nutrition Pro Gainer. But if you don’t mind shelling out extra money for more calories, Serious Mass is worth considering. 

Serious Mass vs Pro Gainer: Final Thoughts

As a skinny person who needs more calories each day, I lean towards choosing Serious Mass over Pro Gainer. 650 calories per serving from Pro Gainer can still help me gain weight, but 1250 calories per Serious Mass shake will make it much easier for me to hit a caloric surplus.

I also love the fact that Serious Mass already contains 3g of creatine monohydrate. This way, I don’t really have to purchase a separate creatine supplement for my bulking diet.

Protein-wise, Pro Gainer may give me just a bit more than what Serious Mass offers. But I can easily boost the protein content of my Serious Mass shake by adding oats, peanut butter, or milk to my drink.

Optimum Nutrition Serious Mass Is The Right Choice If You Are:

  • A hard gainer who is looking for more calories and carbs
  • Someone who prefers to have creatine monohydrate in their shake
  • Someone who wants to have more flavors to choose from

Optimum Nutrition Pro Gainer Is The Right Choice If You Are:

  • A casual gainer who only needs moderate amount of calories and carbs
  • Someone who is on a limited budget
  • Someone who wants high amounts of protein
  • Someone who might need help digesting nutrients

Do you think taking Optimum Nutrition Pro Gainer is enough for building a monstrous physique? Or do you think Optimum Nutrition Serious Mass will do a much better job?

Imad Deryan

My name is Imad, and I struggled to gain mass in the past due to my metabolism and being very skinny. In this blog, I share the best reviews and advice when it comes to gaining weight and mass, for all the people that are struggling like I was.

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