Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer
by Optimum Nutrition
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Optimum Nutrition Serious Mass is one of the market's most established mass gainers, delivering approximately 1,250 calories and 50g protein per two-scoop serving alongside creatine, glutamine, and a full vitamin/mineral blend. Best for Hard gainers struggling to reach calorie targets through food alone and People with poor appetite or difficulty eating enough (e.g. medical reasons).
According to the AIScored 0–100 scoring system, Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer by Optimum Nutrition scores 72.0/100, ranking #4 out of 23 products in Mass Gainers (2026). Strongest category: Effectiveness (80.0/100). Weakest: Side Effects (58.0/100).
Is Optimum Nutrition Serious Mass P... worth buying?
“Optimum Nutrition Serious Mass packs around 1,250 calories and 50g protein per serving, making it a reliable workhorse for anyone serious about gaining weight with proper training. Users consistently report real results—some putting on two stone in three months—and many stick with the brand for a decade or more, which speaks volumes about its effectiveness.”
What Do Reviewers Say About Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer?
Sample excerpts from currently available source material used in this product analysis.
"One word says it all "Marvellous". First class, does exactly what is stipulated on container, I find the 5.4kgs sufficient for all the nutrients one needs to stay well and if needed for a controlled modern lifestyle, I am 71 yrs old and fin..."
"Just tried. My first try now taste good I like it but at half bottle of drink I start feeling my head heavier. I guess I have to use only one scoop instead of 2 scoops."
"Verify good. Yes I have put on kilos on am beater good very tahnk you there's a bit stronger ones like. ultra strong on massive mass strongerrrr yesssss good 10 pocent to2 ultra strong in mass protein thanks youuuuuuuuuuuu love internationa..."
"Lovely. Bought the strawberry flavour, tastes very nice just like having a strawberry milkshake, put on a few 1lbs aswell"
"I contacted Optimum Nutrition customer care to correct my shipping address—a simple request that should have taken minutes. Instead, I was met with extremely rude behavior from the representative. They were dismissive, unhelpful, and repeat..."
How does Optimum Nutrition Serious Mass Protei... score?
Detailed score breakdown and key findings from our analysis of 14 reviews across 3 sources.
Pros
- +Highly effective for calorie surplus and weight gain, with multiple reviewers reporting measurable mass gains (e.g. 2 stone in 3 months with training)
- +Strong long-term loyalty — several reviewers report 5–10+ years of consistent use
- +Good flavour profile (strawberry and banana rated as milkshake-like)
- +Excellent calorie density (1,250 kcal/serving) makes it practical for those who struggle to eat enough food
- +Comprehensive formula includes creatine, glutamine, and 25+ vitamins/minerals beyond basic protein
Cons
- -Inconsistent quality between batches — at least one reviewer reported a virtually flavourless delivery
- -Mixing challenges: oversized scoop won't fit most shaker bottles, and blender is often needed to avoid clumping
- -Digestive discomfort (bloating, gas, heaviness) reported by multiple users — typical of high-maltodextrin mass gainers
- -Premium price point relative to own-brand alternatives, though most reviewers consider it justified
Best For
Watch Out
- !Very high sugar and maltodextrin content — not suitable for those managing blood sugar or insulin sensitivity
- !Gas and bloating reported fairly frequently; start with one scoop to assess tolerance
- !Scoop size requires a blender or large shaker — not convenient for on-the-go use
- !Batch-to-batch flavour inconsistency noted; consider buying smaller sizes first if trying a new flavour
What is Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer?
Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer is a mass gainers product by Optimum Nutrition, scoring 72.0/100 on AIScored.
- • High-calorie mass gainer protein powder with added vitamins, creatine, and glutamine.
- • Designed for those looking to gain lean muscle mass and support recovery.
How We Score Supplements
Our methodology analyses review data, ingredient science, and product information, then scores each product on a 0-100 scale across evidence-based categories:
Effectiveness
How well the product delivers its claimed benefits, based on reviews and ingredient evidence.
Ingredient Quality
Bioavailable forms, clinically effective dosages, clean label, minimal fillers.
Value for Money
Price relative to ingredient quality, dosage count, and effectiveness.
Side Effects Profile
Higher score = fewer side effects. 100 means virtually no adverse reactions reported.
Certifications & Testing
Third-party lab testing, GMP certification, and independent quality verification.
Overall Score
Weighted combination of all factors. Our bottom-line recommendation.
How Does Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer Compare?
See how this product stacks up against the top-rated mass gainers in our database.
| Product | Score | Price |
|---|---|---|
| Optimum Nutrition Serious Mass P... (this) | 72.0 | £52.95 |
| Critical Mass Professional Lean ... | 80.0 | £40.00 |
Price History (90 days)
Frequently Asked Questions
Is Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer worth buying in 2026? ▼
What is the best price for Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer in the UK? ▼
What are the pros and cons of Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer? ▼
How does Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer compare to Critical Mass Professional Lean Mass Gainer Banana 2.4kg (16 Servings)? ▼
Disclaimer: AIScored provides research-backed summaries based on publicly available reviews and product information. This is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Affiliate links may earn us a commission at no extra cost to you.
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