Optimum Nutrition Pro Gainer Review

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Written By
Andy Williams
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ON Pro Gainer is Optimum Nutrition’s alternative to Serious Mass for people who don’t need an extremely high-calorie weight gainer. 

It has 650 calories, 60g of protein, and 85g of carbs per serving. I decided to pick up a bag of their Double Chocolate flavour and give it a try for myself.

What follows is a full Optimum Nutrition Pro Gainer review that covers taste, mixing, and ingredient quality.

UPDATE: Pro Gainer is no longer available. Click here to see the best alternative instead.

ideal for weight gain
Optimum Nutrition Pro Gainer
A bag of Optimum Nutrition Pro Gainer
Taste: 8.4/10
Mixability: 8.3/10
Ingredient Quality: 9/10
Mass-Building Potential: 9/10
Overall Rating: 8.7/10
  • Contains 650 calories per serving—great for lean bulking
  • Has an excellent carb-to-protein ratio (85g of carbs and 60g of protein)
  • Only has 8g of fat
  • Contains just 4g of sugar
  • Tastes quite good for a mass gainer
  • Includes 22 vitamins and minerals
  • Only uses maltodextrin for carbs
  • On the pricey side

Optimum Nutrition Pro Gainer Nutrition Facts and Ingredient Label

First things first, what’s actually inside ON Pro Gainer?

Let’s start with the protein. Optimum Nutrition Pro Complex Gainer boasts 60g of protein per serving, which consists of whey concentrate, whey isolate, whey peptides, calcium caseinate, and egg whites.

Pro Gainer strikes the ideal balance between fast-acting and slow-digesting protein so that you get a potent yet sustained release of amino acids into the bloodstream.

Tubs of Pro Gainer by Optimum Nutrition

Whey protein digests super quickly and really supercharges muscle protein synthesis. However, the massive spike quickly dies off, which is why whey is typically used after a workout, before you eat a post-workout meal.

Egg whites and calcium caseinate, on the other hand, digest much more slowly. And although they don’t create the same protein synthesis spike as whey, they maintain muscle protein synthesis over a longer period of time.

So in combination, these protein sources keep your body in an anabolic state, which is what ultimately leads to hypertrophy.

In terms of carbs, ON Pro Complex Gainer has 85g of carbohydrates per serving. It’s a shame that these carbs seem to be purely from maltodextrin, but I like that the carb-to-protein ratio isn’t too high, which is ideal for lean bulking.

In addition to 22 different vitamins and minerals for overall health, Pro Gainer also has 8g of fat. It’s good to have some fat in your gainer but not so much that it dramatically slows down the absorption of the protein and carbs.

How Effective Is Optimum Nutrition Pro Gainer?

It depends on how many extra calories you need.

If you’re a really hard-gainer, then the 650 calories contained in Pro Gainer might not suffice for your fast metabolism.

On the other hand, if you’re lean bulking and have a decent appetite, then Pro Gainer can give you that extra boost of quality calories, carbs, and protein to get you growing.

While Pro Gainer has a very simple ingredient list (i.e. no added creatine or anything like that), it contains everything you need to build muscle and bulk up.

That said, Pro Gainer won’t do the work for you. If you want these extra calories to turn into hard muscle rather than fat, then you need to spend plenty of time in the weight room.

Also, make sure to drink Pro Gainer in addition to your usual meals and not instead of them. Some people switch out a meal for a mass gainer and wonder why they can’t gain weight!

The whole point of a mass gainer is to give you the extra calories that, for whatever reason—be it time or a lack of appetite—that you’re not getting through your regular diet.

How Does Optimum Nutrition Pro Gainer Taste and Mix?

A tub of ON Pro Gainer

As the Optimum Nutrition Pro Gainer reviews from customers will tell you, this gainer tastes really good and mixes easily, which is as much as you could ask for.

Now, I’m not going to pretend that I was in milkshake heaven while drinking Pro Gainer, but it really does taste good for such a high-calorie supplement.

But because this isn’t a mega-calorie gainer, the texture isn’t too grainy, meaning that the powder also mixes very easily.

I went for Double Chocolate, but I’ve also heard good things about Vanilla. Either way, both are classic protein shake flavours, so you can’t go wrong really.

As a side note, you don’t need to use milk to make Pro Gainer taste good. Unlike some other products, Pro Gainer tastes good with just tap water, which shows that Optimum Nutrition really knows what they’re doing in the flavour department.

How To Use ON Pro Gainer Properly

Using ON Pro Gainer couldn’t be more simple. The real trick is knowing when to take it for the fastest and best results.

To make a Pro Gainer shake, simply add 1 heaping scoop (165g of powder) to between 450 and 500 ml of water (always fill your shake cup with liquid before adding any powder).

Pro Gainer is low-calorie enough that it mixes okay in a standard shaker bottle. But for best results and a lump-free shake every time, you’ll want to use an electric blender, which also opens the door for extra ingredients like peanut butter and berries.

As for when to take Pro Gainer, you can use it anytime you want to consume extra calories, be it at breakfast, between meals, on your lunch break, or before bed.

That said, most people tend to drink Pro Gainer after their workout because it has plenty of protein and a good amount of carbs, which helps to kickstart the muscle recovery process.

Are There Any Downsides To Optimum Nutrition Pro Complex Gainer?

Although Optimum Nutrition Pro Complex Gainer is a quality supplement, it’s definitely not for everyone. But how about side effects?

Well, this goes for any weight gainer, but when you drink Pro Gainer for the first time, you might feel a bit bloated because you’re drinking 650 calories in a very short space of time.

This full feeling will lessen as you get used to drinking mass gainers on a regular basis.

Additionally, if you were to consume too many servings of Pro Gainer, you might gain unwanted body fat. However, this would be as a result of overall caloric excess and not Pro Gainer specifically.

Since Pro Gainer has a very simple ingredient list, there isn’t really much to watch out for. It’s a very clean supplement without any fillers (though I still feel that it relies too heavily on maltodextrin).

Is ON Pro Complex Gainer Good Value For Money?

A bag of Optimum Nutrition Pro Gainer

While ON Pro Complex gainer isn’t cheap, it’s pretty good value for money because you’re getting loads of protein per serving. To put it another way, you’re not just paying for cheap carbs, though Pro Gainer does make liberal use of maltodextrin as well.

You can also see my Gold Standard Mass Gainer review if you’d like to see another Optimum Nutrition supplement that’s very similar to ON Pro Gainer.

Because Pro Gainer has 60g of quality protein per serving, you might be able to get by without taking any protein shakes when using this supplement, especially if you’re eating a good amount of protein from whole food sources.

So, although Pro Gainer is expensive, it can be pretty good value overall if it means saving money on whey protein powder.

See Also:

Conclusion: Is Pro Gainer By Optimum Nutrition a Good Product?

As you can see from my Optimum Nutrition Pro Gainer review, I’m definitely a fan of this supplement overall. It has everything that you need to put on quality muscle, whether you’re lean bulking, looking to recover faster after a workout, or trying to cram in as many calories as possible.

Yet, if you’re a really hard gainer, then you might be better off with a higher-calorie formula.

Additionally, I think that there are better weight gainers out there in this price range.

Pro Gainer does nothing wrong, really—except perhaps relying slightly too much on maltodextrin for its carbs. However, the mass gainer market has dramatically improved in recent years, and I think the competition has caught up and, in some cases, surpassed Pro Gainer. 

That’s just my honest opinion.

Overall, ON Pro Gainer is a solid option—you can’t go wrong with Optimum Nutrition products. However, before committing to a full bag, you might want to try a smaller tub first and check out the other options.

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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