Optimum Nutrition Serious Mass Protein Powder High Calorie Mass Gainer vs Critical Mass Professional Lean Mass Gainer Vanilla 6kg (40 Servings)

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

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

Pros

• ✓Over 1,000 calories per serving — highly efficient caloric surplus for hard gainers
• ✓Premium protein source: ISO-XP 95% Whey Protein Isolate at 42g per serving
• ✓Evidence-based performance additions: creatine monohydrate, HMB, leucine, and glutamine
• ✓Reduced-sugar formulation compared to conventional mass gainers

Cons

• ✗Batch-to-batch flavour inconsistency reported — some users find later purchases taste synthetic or chemical
• ✗Large 150g serving size can clump without a blender; shaker alone may not suffice
• ✗Contains milk, soy, and wheat — unsuitable for those with common allergens
• ✗Very high caloric density requires careful tracking to avoid unwanted fat gain

Best For