Optimum Nutrition Pro Gainer

For some people, gaining weight can be difficult for a variety of reasons. It could be because they have a small appetite and find it difficult to eat big portions, because the cost of a bodybuilder bulking diet is high, or simply because they have a high metabolic rate. Optimum Nutrition Pro Gainer is a high-calorie weight gain supplement designed to help people who want to gain weight or bulk up, to get the calories they need to meet their goals.

Below we take an in-depth look at the benefits offered by Optimum Nutrition Pro Gainer.

Optimum Nutrition Pro Gainer Pros

  • Money-back guarantee offered (within fair use policy)
  • Positive customer reviews
  • Will help quick weight gain

Optimum Nutrition Pro Gainer Cons

  • Customer complaints about taste
  • Expensive
  • Full details of Individual ingredient quantities not provided
Watchdog Rejected

Optimum Nutrition Pro Gainer


What You Need To Know About Optimum Nutrition Pro Gainer

Optimum Nutrition Pro Gainer is a high calorie bulking powder that is designed to help consumers gain weight fast. Each serving (1.5 scoops) contains 60 grams of protein, 85 grams of carbohydrates and a total 650 calories. The product comes in a range of different flavours, including banana cream, cookies and cream, double chocolate, strawberry, and vanilla custard.

The product comes in two sizes- a 5lb bag and a 10lb bag. The large bag contains 28 servings, and the small bag contains 14 servings. The main ingredient is Maltodextrin, a highly processed starch that can cause blood sugar levels to rise very quickly. The rest of the ingredients are a variety of different protein sources.

What Are The Side Effects Of Optimum Nutrition Pro Gainer?

Some of the ingredients found in Optimum Nutrition Pro Gainer could cause a range of side effects.

Whey protein can cause some side effects, including increased bowel movements, diarrhoea, nausea, thirst, stomach cramps, fatigue, and bloating.

Maltodextrin has a very high GI rating and can raise blood sugar levels very quickly. This means that this supplement is unlikely to be suitable for diabetics.

How Much Does Optimum Nutrition Pro Gainer Cost?

Optimum Nutrition Pro Gainer can be purchased directly from the official Optimum Nutrition website; a 5lb bag (14 servings) costs $39.99, and a 10lb bag (28 servings) costs $69.99. Delivery charges may apply.

The supplement is also available from numerous third-party online retailers. Prices vary, and so it definitely pays to shop around! Some stores only carry a limited selection of flavours.

Our Verdict On Optimum Nutrition Pro Gainer

The main ingredient in Optimum Nutrition Pro Gainer is maltodextrin, and ultimately the purpose of the supplement is to make consuming an incredibly large number of calories easier, quicker, and more convenient.

The product is suitable for use during a bulking phase but is far from ideal for use during a cutting phase. Maltodextrin can cause significant blood sugar spikes and this supplement is not suitable for diabetics. In general, Optimum Nutrition Pro Gainer is suitable for purpose, as it will help consumers to get more calories in their diet and ultimately gain weight.

The number of flavour options means that there is plenty of choice for customers, but there are a significant number of negative comments about the flavour profiles.

The product is covered by a very generous returns policy; there is a limit to the guarantee, but as it is a fair use policy and consumers can return opened and used products (as long as 75% of the product or more remains) we are more than happy with this policy. The supplement is very expensive costing around $40 for just 14 servings.

Overall, we do not recommend Optimum Nutrition Pro Gainer to our readers.

Optimum Nutrition Pro Gainer Review

Optimum Nutrition Pro Gainer is a high-calorie protein supplement that is designed to assist with weight gain. Each serving contains 650 calories. This is a similar product to Optimum Nutrition Serious Mass, but has far fewer calories per serving, a much lower maltodextrin content, and is far more expensive.

Optimum Nutrition Pro Gainer Facts

  • Manufactured by Optimum Nutrition
  • Choice of 5lb or 10lb bags
  • 14 or 28 servings per bag

Optimum Nutrition Pro Gainer comes in a range of flavours, including vanilla custard, double chocolate, banana cream, strawberry, and cookies and cream.

How to Take Optimum Nutrition Pro Gainer

Directions for use are as follows:

  • Add 1 heaping scoop to about 16 oz of cold water and shake or blend for 45-60 seconds. Mix with milk and ice in a blender for a thicker shake. It can be taken between meals or after a workout, depending upon your needs
  • Between Meals: Drink 1-2 serving(s) between meals to support a high-calorie diet
  • Post-Workout: Drink 1 serving of Pro Complex Gainer 30-60 minutes following exercise to support maximum recovery

Pro Gainer is manufactured by Optimum Nutrition, an American company who are based in Downers Grove, Illinois. They can be contacted using the information on their official website, or using any of their social media pages, which are all active and maintained. Optimum Nutrition claims that they maintain a “Gold Standard”, with strict standards for “ingredients selection, quality control, lab testing and manufacturing processes”.

Optimum Nutrition Pro Gainer Concerns:

  • Customer complaints about taste
  • Maltodextrin can cause quick increases in blood sugar levels
  • Expensive supplement

What Does Optimum Nutrition Pro Gainer Claim To Do?

Optimum Nutrition describes Pro Gainer as a high-calorie, high protein formula, suitable for use as a “high protein meal between meals”, or as a post-workout recovery shake. In addition to the high protein content, the product also contains 85 grams of carbohydrates per serving, primarily sourced from maltodextrin, which is intended to help restore energy levels.

Does Optimum Nutrition Pro Gainer Work?

If your main goal is to gain weight, then Optimum Nutrition Pro Gainer will most definitely help you to achieve your goals. If you are trying to gain muscle mass, then obviously it is important to follow the correct muscle building exercises as well. A sedentary person consuming this product on top of their normal food will definitely just gain fat mass (as seen in some customer reviews).

What Are The Ingredients of Optimum Nutrition Pro Gainer?

The ingredients found in Optimum Nutrition Pro Gainer are detailed below. Each serving of 1.5 scoops (169 grams) contains 60 grams of protein, 85 grams of carbohydrates, 8.8 grams of fat, and 5.4 grams of fibre. Each serving provides a total of 650 calories.

  • Maltodextrin: Maltodextrin is the main source of carbohydrates and calories in this supplement. Maltodextrin is a highly processed starch that typically is made from corn, rice, potato starch, or wheat. Although it is usually used as a thickener, filler, or preservative in foods, here it is the main ingredient. It will help to replenish the body’s glycogen and glucose levels. Source

Protein Blend

  • Whey Protein Isolates [With Emulsifier: Soy Lecithin]: Whey seems to help recovery after sports and endurance training so is often used by athletes. Whey protein contains BCCA amino acids and may cause feelings of satiety. It appears to decrease the release of hormones such as ghrelin, which signals hunger.
  • Whey Protein Concentrate: See above. Whey Protein Concentrate is digested slightly slower than Whey Protein Isolate, and has a higher fat and carbohydrate content than Whey Isolates. Source
  • Calcium Caseinate: A source of protein, calcium caseinate breaks down slower than whey proteins, meaning that it can provide a sustained release of amino acids over time. Source
  • Egg Albumen: Known as egg white.
  • Whey Peptides
  • Wheat Protein [Glutamine Peptides]

Lipid Blend

  • Medium Chained Tri-Glycerides: MCTs are found naturally in coconut oil and palm kernel oil (amongst others). Research suggests that these useful fats increase serum ketone levels to a greater extent than all other fatty acids. They have also been found to cause a small boost in metabolism, and may decrease fat mass to a greater extent than other long chain fatty acids. Source
  • High Oleic Sunflower Oil


  • Partially Hydrolysed Guar Gum, Soy Lecithin.

Mineral Blend

  • Sodium Chloride, Ferric Pyrophosphate, Zinc Oxide, Manganese Sulphate, Copper Gluconate, Chromium Chloride Hexahydrate, Potassium Iodide, Sodium Molybdate.

Enzyme Complex

  • Amylase, Protease, Cellulase, Beta-D-Galactosidase, Lipase.

Vitamin Blend

  • Dextrose Monohydrate, Ascorbic Acid, Vitamin E Acetate, Niacinamide, Biotin, Vitamin A-Acetate, Calcium-D-Pantothenate, Pyridoxine Hydrochloride, Folic Acid, Cholecalciferol, Thiamine Hydrochloride, Riboflavin, Vitamin B12.


  • Sucralose, Acesulfame Potassium.


  • Mixed Tocopherols.

Does Optimum Nutrition Pro Gainer Have Any Side Effects?

Protein Powders are usually unlikely to cause side effects, but Pro Gainer is a “gainer” supplement that is very high in protein and other ingredients that could cause more side effects than your average protein shake.

Whey protein can cause some side effects, including:

  • Increased bowel movements
  • Diarrhoea
  • Nausea
  • Thirst
  • Stomach cramps
  • Fatigue
  • Bloating

Maltodextrin has a very high GI rating and can raise your blood sugar levels very quickly. This means that this supplement is unlikely to be suitable for diabetics. Signs that maltodextrin has caused your blood sugar to spike include a sudden headache, increased thirst, trouble concentrating, blurred vision, and fatigue. If you experience any of these symptoms, check your blood sugar levels immediately. If they’re too high, contact your doctor.


Not suitable for pregnant or breastfeeding women. Not suitable for anyone under the age of 18. Not suitable for anyone who is allergic to wheat, gluten or whey. Not suitable for diabetics. Consult your doctor if you are unsure about the suitability of this supplement for you.

Are There Any Customer Reviews For Optimum Nutrition Pro Gainer?

There are well over 1300 customer reviews for this product on Amazon, with over 70% of them being rating five stars. Many of the negative reviews are concerning the poor taste of individual flavours. Numerous customers recommend weighing out servings rather than using the recommended “heaping scoop”, which they found to be an ineffective measuring device.

Terrible artificial taste. Nasty stuff. Tried one glass. Will not use.

Awesome protein but an inaccurate serving size

This really does it’s job. Took it with whole milk and a banana, gained 10 pounds after the fist bottle. But I was lazy to work out so most of the growth went towards stomach area. Now I have a big belly even with empty stomach. So better work out for even weight distribution if u want to try this product.

Tasty and it’s a good product – however, very expensive for a simple weight gainer. It’s relative a high ingredient product compared to other weight gainers I tried before, but it’s way too expensive. Pretty hard to keep up with it due to its price.

Does Optimum Nutrition Pro Gainer Offer a Money-Back Guarantee?

Optimum Nutrition supplements that are purchased from the official Optimum Nutrition website are covered by a generous returns policy, which lasts for 30 days from the date of purchase. Some opened products are accepted, but only if less than 25% of the product has been used. This policy allows customers to try the product out without risk, but prevents abuse of the returns policy. Customers should contact Optimum Nutrition to get an RMA code before sending products back to the company.

The returns policies of third-party retailers may vary.

Where Can I Buy Optimum Nutrition Pro Gainer?

Pro Gainer can be purchased directly from the official Optimum Nutrition website; a 5lb bag costs $39.99, and a 10lb bag costs $69.99. Delivery charges may apply.

The supplement is also available from numerous third-party online retailers. Some stores only carry a limited selection of flavours.

iHerb sells a 5lb bag for $55.99 plus delivery charges.

Predator Nutrition, a UK-based online retailer, charge £43.99 for a 5lb bag (2350g) and £77.99 for a 10lb bag (4400g). Delivery charges may also apply.

Summary: Optimum Nutrition Pro Gainer

Optimum Nutrition Pro Gainer

2.7 out of 5
Optimum Nutrition Pro Gainer Rating

The Muscle Watchdog does not recommend Optimum Nutrition Pro Gainer.

  • Effectiveness
  • Safety
  • Price / Guarantee

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Disclaimer: Our reviews and investigations are based on extensive research from the information publicly available to us and consumers at the time of first publishing the post. Information is based on our personal opinion and whilst we endeavour to ensure information is up-to-date, manufacturers do from time to time change their products and future research may disagree with our findings. If you feel any of the information is inaccurate, please contact us and we will review the information provided.

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