Serious Mass vs Pro Gainer: Comparing 2 Weight Gain Powders

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Serious Mass vs Pro Gainer - weight gain powder comparison - heydayDo featured image

In this article I discuss the similarities & differences that exist between Optimum Nutrition’s two popular weight gain powders, Serious Mass & Pro Gainer.

If you’re considering taking either of them, note that there are sharp distinctions in key categories such as calories, macronutrient profile, workout performance enhancers, vitamins, and minerals.

Besides going over all of those areas, in Serious Mass vs Pro Gainer we’ll also be looking at the powders’ respective carbohydrate & protein sources as well as practical things like serving size and online buyer ratings.

test tubes green - heydayDo icon

Science resources included

As is my custom here on heydayDo, I will provide links to all of the relevant sports science and medical resources, clinical studies, & nutritional data used in this article.


What’s coming up

I’ll save the nutritional comparisons — calories, macros, ingredients — for later, and first have us look at the basic stuff: serving size & buyer ratings.

I think it’s important to know that the big difference in serving size between Serious Mass & Pro Gainer impacts many of the other comparisons in this article.

Knowing the serving size disparity ahead of looking at all of the nutrient & cost information will help us keep the right perspective when we get to those things.

Optimum Nutrition Serious Mass Weight Gainer Protein...
  • High calorie weight gainer: 1,260 calories per 2-scoop serving
  • 50 grams of blended protein per serving
  • Over 250 of carbohydrates per serving

Last update on 2024-04-18 / Affiliate links / Images from Amazon Product Advertising API

Optimum Nutrition GS Pro Gainer Weight Gainer Protein...
  • Vitamin C and Zinc Provides Immune Support along with Vitamin E
  • 650 CALORIES - delivering calories that count to support your gains
  • 60G PROTEIN BLEND - support your mass gaining goals with high-quality...

Last update on 2024-04-18 / Affiliate links / Images from Amazon Product Advertising API

In the section where I compare Pro Gainer’s nutrient profile to Serious Mass’, I’ll be going over the following categories:

  • Calories
  • Macronutrients
  • Ingredients, including
      • additional fitness supplements
      • vitamins & minerals
  • Carbohydrate sources
  • Protein sources

I’ll also share some of the current sports science research related to the importance & specifics of post-workout nutrition, since Optimum Nutrition markets both of these mass gainers as not only calorie boosters, but also as post-workout recovery products.


Program note

Any time you see Serious Mass’ & Pro Gainer’s images or their names written in blue, those are links to their respective Amazon product pages that you can click on to check current price, read buyer reviews, etc…and those pages will open in a separate browser tab.

Also, there are very slight price & ingredient differences amongst the various flavors Serious Mass & Pro Gainer each come in.

And so all of the nutrition info I’m providing I’m getting from their chocolate flavored versions, though with cost I looked for the cheapest flavor (for example, Pro Gainer’s Vanilla Custard in the 10 lb. bag size).


Serving size – Pro Gainer vs. Serious Mass

For this article I bought a 6 lb. tub of Serious Mass’ Vanilla flavor, and the 5 lb. tub of Pro Gainer’s chocolate:

Serious Mass vs Pro Gainer Chocolate - heydayDo image


And here’s a head-to-head look at their serving sizes, snipped off of product pages:

Serving size comparison between ON's Serious Mass and Pro Gainer powders - heydayDo image


The ‘scoop(s)’ on Pro Gainer & Serious Mass servings

After sticking my hand in each one & fishing around down in the powder ’til I got the scoops out, I discovered that Serious Mass & Pro Gainer use the same scoop.

ON's Serious Mass and Pro Gainer powders use the same scoop - heydayDo image

So that explains how Serious Mass’ serving size of 336 grams is close to exactly double Pro Gainer’s 165 grams, since Pro Gainer’s serving size is listed as one heaping scoop, and Serious Mass’ serving size calls for two heaping scoops.


But the powders don’t weigh the same…

I put the same amount of each powder into their scoop — they were both packed firm by me scraping it up the inside wall of the tub and then very slightly rounding it.

But Pro Gainer weighed 15 grams less, even with me heaping it up a little more than I did with the Serious Mass:

Weight comparison of 1 scoop of Serious vs Pro Gainer - heydayDo image

Serious Mass weighing in at 168 grams per rounded scoop, and Pro Gainer at 153 grams.


I can pass along to you that Serious Mass has a denser feel & look than Pro Gainer powder when you check them out side by side.

And my guess is because its got a ton of maltodextrin in it while Pro Gainer backs off the maltodextrin and has more whey protein in it — which by nature is light & fluffy when in powder form.

Since the term heaping is vague and its execution not real smooth**, I took a smaller scoop from a random whey powder tub I had and packed it (pretty) evenly with Serious Mass & Pro Gainer and weighed them.

Got the same result: Serious Mass weighs more.

Weight comparison of Pro Gainer vs Serious Mass using a level MuscleTech scoop - heydayDo image

**Heap big mess

By the way, I couldn’t get 165 grams — Pro Gainer’s serving size — to stay on top of the scoop, and I tried 3 times.

The closest I got was 153 grams, but even that was a little messy.

You can see from the earlier image above that at 153 grams it’s already spilling off, and a bunch of it is just waiting for me to make a wrong move so it can fall off too.

But the Serious Mass hit its 1/2 a serving (168 grams) pretty easily, just from getting it packed in while scooping inside the tub.


The Pro Gainer & Serious Mass scoop is BIG

From the images below you’ll see that it stands almost 3″ high, and that it’s way bigger than the Optimum Nutrition Gold Standard Whey scoop it swallowed up.

Size of scoop that comes with Serious Mass and Pro Gainer - heydayDo image

Serving suggestions: Serious Mass vs. Pro Gainer

The difference in the powder consistency between Serious Mass & Pro Gainer I mentioned earlier has an effect on the directions Optimum Nutrition gives us when it comes to making the beverages.

Here’s a bullet-pointed summary for each of them.


Serious Mass directions for use

  • Use a blender**, not a shaker bottle;
  • 24 oz. of liquid;
  • They suggest starting with one scoop (168 grams).

** – Personal note: I agree with Optimum Nutrition about going the blender route. I used only a 1/6 dose (51 grams) in a shaker bottle and I couldn’t get rid of all the clumps, despite a lot of additional aggression after the first couple of taste tests. 😄

Optimum Nutrition Serious Mass directions for use - heydayDo image

Pro Gainer directions for use

  • They suggest a shaker** or a blender;
  • 16 oz. of liquid, so Serious Mass needs a cup more than this.

** – My take: I did a 1/4 dose (41 grams) in a shaker bottle with around 12 oz. of water & it blended well with the same number of shakes I’d give a regular protein powder.

I couldn’t test out a full serving that way because my shaker bottle only holds a little over 16 oz. of liquid, so the 165 grams of powder won’t even fit.

Optimum Nutrition Pro Gainer directions for use - heydayDo image

Cost per serving – Pro Gainer v. Serious Mass

Like I usually do, just wanted to let you know I’m using the prices I’m looking at today, and that you may see something  different when you look them up — hopefully you’ll see a “20% off” sale. 😉


Cheapest places to buy ON’s Serious Mass & Pro Gainer

Serious Mass prices

As of today anyway, Amazon has the best deal on Serious Mass — the 12 lb. bag of Chocolate flavor is listed around 77 bucks (40¢ per oz.), while over on Optimum Nutrition’s website I see that it’s selling for $99.


Pro Gainer prices

Today I see that  that the ten lb. bag of Vanilla Custard on Amazon is going for $116 & change (71¢ per oz.)

And over on Optimum Nutrition’s website Pro Gainer’s 10 lb. bag is only being sold in bundles with other items, and their 5 lb. tub is $76.


About the Serious Mass vs. Pro Gainer cost per serving comparison

Note that Serious Mass & Pro Gainer have different large sizes (12 lb. & 10 lb., respectively) as well as different small sizes (6 lb. & 5 lb., respectively).

So for my cost per serving illustration I’ll just separate them as “large” or “small”.


Large Sizes

ON Serious Mass Gainer powder

Serious Mass 12 lb. cost: $77

Servings: 16

Cost / serving: $4.81


ON Gold Standard Pro Gainer Powder

Pro Gainer 10 lb. cost: $116

Servings: 28

Cost / serving: $4.14


You can see that Pro Gainer is about 70¢ cheaper, which comes out to $21/month less if you were planning on drinking 1 serving per day.


Small sizes

ON Serious Mass Gainer Powder 6 lb.

Serious Mass 6 lb. cost: $45

Servings: 8

Cost / serving: $5.63


ON Gold Standard Pro Gainer Powder 5 lb.

Pro Gainer 5 lb. cost: $71

Servings: 14

Cost / serving: $5.07


Serious Mass vs. Pro Gainer cost comparison summary

As we all probably figured, the larger sizes of these mass gainers are a better deal for your wallet.

As far as which of these two is a better deal for each of us, well that I think comes down to our individual fitness goals.

For example, someone may think the 12 lb. bag of Serious Mass ($4.81/serving) isn’t as good of a deal as the 10 lb. Pro Gainer (@ $4.14/serving), but that’s only if they intend to take Serious Mass’ full serving size of 336 grams & all of its 1,250 calories.


If you:

* are pumping iron regularly with some intensity, and

* really want to add the pounds quickly, and

* can handle 1200+ calories as a BETWEEN MEAL supplement, and

* don’t mind the fact that not all of the weight you’re adding is lean muscle,

then Serious Mass at under 5 bucks a serving may be the best gainer for the job.


Cut it down to half by taking just one scoop — same amount as Pro Gainer’s serving size — and now it’s only $2.40 a pop, and thus around 40% cheaper than Pro Gainer gram for gram.


Bottom line:

And in my humble opinion Serious Mass should be much cheaper than Pro Gainer when we’re comparing them using the same weight, for example one scoop apiece.

This is because around 80% of Serious Mass consists of just one ingredient (maltodextrin) that is very inexpensive to make, and Pro Gainer has over two and a half times the protein as Serious Mass does in a single scoop (60 grams vs. 25).

We’ll get more into these & other ingredients in just a bit, but next let’s compare Pro Gainer’s & Serious Mass’ buyer ratings.



Buyer ratings – Serious Mass vs. Pro Gainer

Bottom line:

* These two mass gainers are both well-regarded by their buyers.

* Serious Mass has been around longer so it has a lot more reviews, plus it’s been the #1 selling mass gainer for a few years running now.

* And it’s more affordable for many people, since as I showed earlier it’s cheaper “gram for gram”, or by the scoop if you prefer ($2.40 vs. $4.14).


About the buyer review numbers

The ⭐ rating you see I calculate after gathering as many online reviews as I can find on the various fitness supplement retailers, and the sign you see represents the percentage of reviewers who gave the product a 4 or 5-star rating.

Generally speaking in the fitness supplement arena, an 80% is like a “B” in school: good not great, and 90% & up is excellent.

I’ve mentioned this elsewhere here on heydayDo: mass gainer ratings — even for the most popular powders — are lower than the ratings you’ll find for the top well-regarded “regular” protein powders.

I’ve read a lot of buyer reviews over the years and here’s my slightly-informed guess as to why this is:

  • some buyers aren’t aware that a gainer is supposed to have a ton of carbs in it;
  • the taste of some gainer flavors ain’t great;
  • the bloat that can come from downing several hundred calories in a short period of time.


Serious Mass buyer reviews

4.5 ⭐  88% 4&5-star ratings,  38,000+ online reviews
ON Serious Mass Gainer powder
Check today’s price & reviews on Amazon


Pro Gainer buyer reviews

4.6 ⭐  90% 4&5-star ratings,  4,000+ online reviews

ON Gold Standard Pro Gainer Powder

Check today’s price & reviews on Amazon


Macros – Serious Mass vs. Pro Gainer

OK, here are the comparisons of per serving calories & macronutrients (protein, carbs, & fat) for these two mass gainers.

I’ll also list the sugar & sodium amounts in this section too, “just cuz”.

I’ll go with the manufacturer’s listed serving sizes, which means two scoops for Serious Mass and one for Pro Gainer.

(Of course the macronutrient percentages for Serious Mass won’t be any different whether you’re drinking it with one scoop or two.)


Calories per serving – Serious Mass vs. Pro Gainer

Serious Mass 1,250

Pro Gainer 650


Protein per serving – Serious Mass vs. Pro Gainer

Serious Mass 50 grams

Pro Gainer 60 grams


Carbs per serving – Serious Mass vs. Pro Gainer

Serious Mass 252 grams

Pro Gainer 85


Fat per serving – Serious Mass vs. Pro Gainer

Serious Mass 4.5 grams

Pro Gainer 8 grams

Optimum Nutrition Serious Mass & Pro Gainer macros - heydayDo image

Sugar per serving – Serious Mass vs. Pro Gainer

Serious Mass 20 grams

Pro Gainer 7 grams


Sodium per serving – Serious Mass vs. Pro Gainer

Serious Mass 570 milligrams

Pro Gainer 380 milligrams


Macronutrient percentages – Serious Mass vs. Pro Gainer

Below is a chart that compares the macronutrient percentages of Pro Gainer & Serious Mass, and you can see the sharp differences in their respective carbs to protein ratios.

Serious Mass is over 5:1 carbs to protein while Pro Gainer is roughly 1.5:1, with Serious Mass delivering the majority of its calories via the high glycemic index carb maltodextrin, & Pro Gainer going with more protein & a bit more fat.

Macronutrient percentages for Optimum Nutrition Serious Mass & Pro Gainer - heydayDo image

Is one mass gainer carb-to-protein ratio better than the other?

In one sense not really, since one of their main purposes is simply to provide significant additional calories in between meals, not be a complete meal replacement.

Remember Optimum Nutrition’s blurb in its directions for Serious Mass use:

Optimum Nutrition Serious Mass directions for use - heydayDo image

Macro ratios usually act as daily intake guidelines

I’m not positive, but I think the concept of macro percentages ever getting into our heads started with simple dietary guidelines that are issued by the National Academies Institute of Medicine.

I have their book Dietary Reference Intakes: The Essential Guide to Nutrient Requirements, and on page 81 of the PDF they list these macronutrient percentages as guidelines for adults:

“45–65 percent of their total calories from carbohydrates, 20–35 percent from fat, and 10–35 percent from protein.”

Keep in mind this is broad advice for the general public, most of whom aren’t as active as athletes & other consistent weightlifters like recreational bodybuilders, workout warriors, etc.


Macro ratios for bodybuilders

There has been some research done to establish macronutrient percentage guidelines for competitive bodybuilders which I think is worth taking a peek at, even though they train a lot more hardcore than the rest of us consistent lifters.

Their numbers:

  • Protein 30%
  • Carbs 55-60%
  • Fats 15-20%


Serious Mass & Pro Gainer for post-workout nutrition

That research paper “Macronutrient Considerations for the Sport of Bodybuilding” published in Sports Medicine I referenced above also talked about the importance of getting amino acids from quality protein along with high glycemic carbs right after weight training, and the amount of suggested high GI carbs was a lot…here’s their concluding quote:


“Consumption of protein/amino acids and carbohydrate immediately before and after training sessions may augment protein synthesis, muscle glycogen re-synthesis and reduce protein degradation.

The optimal rate of carbohydrate ingested immediately after a training session should be 1.2 g/kg/hour at 30-minute intervals for 4 hours and the carbohydrate should be of high glycemic index.”


The amount again is 1.2 grams of high GI carbs per kilogram of bodyweight per hour, taken over a four hour period.

I’m not that regimented enough to follow that schedule, but I know competitive bodybuilders who are/were.

I’m just interested in what’s the total amount of post-workout high GI carbs sports science recommends for the most intense weightlifters, and I’ll just adjust their numbers down to fit my moderate intensity training program.


If I apply their math — a kg is 2.2 lb. — roughly to my weight (180 lb.), then the recommendation is 90 grams four times, which equals 360 grams of high glycemic index carbs.

But that’s for hardcore bodybuilders.

I’m just a recreational lifter, so if I ratchet their numbers down by 30% or so (360 – 110) I end up at 250 grams — which is a Serious Mass single serving.


And indeed, Optimum Nutrition mentions taking both Serious Mass & Pro Gainer post-workout in their respective marketing material:

Optimum Nutrition marketing material saying Serious Mass & Pro Gainer are to be used post-workout - heydayDo image

Post-workout carbs & protein studies

You may have heard that there are certain carb:protein ratios that ought to be targeted post-workout — usually 3:1 or 4:1.

But while there is some sports science research that supports this idea, other post-workout carbohydrate & protein studies conclude that adequate fast-absorbing protein (whey for instance) is good enough on its own. (1)

In any event, while the strength & conditioning scientists debate what the ideal numbers to hit are, it is agreed upon that weightlifters need to load up on key nutrients post-workout.

Here’s a money quote from the International Society of Sports Nutrition:

“It has been recommended that athletes ingest carbohydrate and protein following exercise in order to enhance glycogen re-synthesis, promote an anabolic hormonal environment, enhance protein synthesis, and/or lessen the immuno-suppressive effects of intense exercise.” (2)


Ingredients – Serious Mass vs. Pro Gainer

Optimum Nutrition handles the ingredients listing of Serious Mass & Pro Gainer differently on their Supplement Facts labels, though they share many common ingredients.

Here’s Serious Mass’ Supplement Facts label without the macros section since I showed it to you earlier, and its ingredients list is below it:

Serious Mass vitamins minerals & ingredients - heydayDo image


And here’s the bottom half of Pro Gainer’s Supplement Facts label showing all the vitamin & mineral additives; note its ingredients list below it has all those vitamins & minerals listed again.

Pro Gainer vitamins & minerals plus ingredients list - heydayDo image

Optimum Nutrition doesn’t list all the vitamins added to Serious Mass in its ingredients like they do for Pro Gainer, they just put them on the Supplement Facts label.

Below are my “in a nutshell” of what each of them mainly consist of.


Serious Mass ingredients summary

* Serious Mass is basically high glycemic carbs in the form of maltodextrin plus a protein blend that’s mostly whey with a little casein & egg white too.

* Serious Mass is over 80% maltodextrin, 16% whey/egg protein, and has been fortified with a long list of vitamins & minerals.

* It has a couple of performance enhancer supplements added as well, creatine & glutamine.


Pro Gainer ingredients summary

* Pro Gainer is also high in maltodextrin, but only 56% worth vs. the 82% of it in Serious Mass.

* Pro Gainer’s protein blend (39% of its ingredients) has more whey in it than Serious Mass’, thanks to the addition of whey protein isolate & whey peptides.

* Pro Gainer also has a fleet of vitamins & minerals added to it, though in less quantity overall compared to Serious Mass — but remember, its serving size (1 scoop) is only half the size of Serious Mass’.

* It doesn’t have any fitness supplements added to it like Serious Mass does.


Serious Mass vs Pro Gainer: Taste

You can click on either of the two product images I provided earlier to go read buyer opinions about how these powders taste over on ol’ Amazon.

I’ll pass along that I can tolerate the vanilla-flavored Serious Mass in water, and that I kind of like the chocolate-flavored Pro Gainer — which I’ve also been drinking in water since I bought it for this article.

If you’ve read other protein powder reviews of mine here on heydayDo, you know I don’t believe my opinion on taste provides you any value, since I’m convinced by science & life experiences that our taste buds do not interpret taste the same.

That said, for me the chocolate Pro Gainer was a lot better tasting than that vanilla Serious Mass.

Better texture too, but that’s the difference between a product that’s 39% milk protein (Pro Gainer) vs. one that’s 82% processed carbohydrate (Serious Mass).


Wrapping up

Related articles here on heydayDo

How to Use a Mass Gainer, How It Works, Side Effects, & More

How To Build Muscle & Gain Weight If You’re An Ectomorph

Make Your Own Homemade Protein Shake Recipes for Weight Gain

Does Pre-Workout Work? Only With These 7 Ingredients

7 Pre-Workout Side Effects You Should Be Aware Of

I hope that my article on comparing Optimum Nutrition’s Pro Gainer to their best-selling weight gain product Serious Mass is useful to you, and I wish you well on your fitness journey.

– greg

About The Author

heydayDo author Greg Simon

Hi, I’m Greg Simon. Fitness training & nutrition researching since 1982. ISSN (International Society of Sports Nutrition) Pro Member. MBA, B.Sc.

Author. Surfer. Organic food grower. Congenital heart disease survivor (so far). is my wellness blog that’s about encouraging a healthy lifestyle as we age. 

I share my fitness training experience as well as the sports science research I’ve done on the many benefits strength building, exercise, & good eating habits offer us. 

I also write review articles after product testing and evaluating home gym equipment & fitness supplements.

My hope is that you’ll find useful or encouraging information here on my website that will benefit your unique fitness journey.

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