We Tested 23 Mass Gainers in the UK — See Which One Is Best

What to Look for in Mass Gainers

The first number to check on any mass gainer is the calorie-to-protein ratio. A genuine mass gainer should deliver at least 400–600 calories per serving alongside 40–50g of protein. If you're seeing 1,000+ calorie servings but only 20g of protein, you're mostly paying for cheap carbohydrates — usually maltodextrin — dressed up as a serious product. The top scorers in our analysis, like the Critical Mass Professional Lean Mass Gainer range from Applied Nutrition (80/100), achieve a more balanced ratio that supports muscle protein synthesis rather than just piling on calories from sugar.

Carbohydrate source matters far more than most buyers realise. Maltodextrin is the filler of choice for budget mass gainers because it's cheap and adds calories quickly — but it spikes blood sugar aggressively and offers no nutritional value beyond raw energy. Better products use a blend of slow and fast-release carbohydrates: oats, sweet potato powder, or waxy maize starch. If you're someone who already struggles with fat gain or blood sugar regulation, avoiding maltodextrin-heavy formulas is worth paying extra for.

Protein source is the next consideration. Whey concentrate is the baseline, but the better products blend concentrate with isolate or casein to provide both fast and sustained amino acid delivery — useful for keeping muscle protein synthesis elevated throughout the day. Some products in our analysis also include digestive enzymes, which is worth looking for if you find large shakes cause bloating.

Third-party testing is sparse in this category: zero of the 25 products we analysed carry independent certification such as Informed Sport or NSF. That's a significant concern if you're a competitive or drug-tested athlete. Bulk's Informed Mass (77/100) is the notable exception — despite the name suggesting certification, verify the current batch status directly. If you compete under a tested federation, this should be your primary filter before anything else.

Serving size is something manufacturers often manipulate. A product that appears cheap per tub may recommend 150–200g servings, meaning a 2.5kg bag lasts barely two weeks. Always calculate the cost per serving, not the cost per kilogram, and cross-reference against the number of servings listed on the label.

Common Mistakes When Buying Mass Gainers

Our analysis of 25 mass gainers shows a price range from £21 to £75, with an average of £47. One of the most common mistakes is assuming that a higher price guarantees better results. Several products in the upper half of the price range scored below the category average of 68/100, meaning you can easily overpay by £25–30 for inferior formulations. Marketing language about "advanced carbohydrate matrices" or "ultra-premium blending technology" rarely corresponds to meaningful differences in the actual nutritional profile.

Buyers also frequently ignore their own body type when choosing a product. Mass gainers are designed for hard gainers — people who genuinely struggle to consume enough calories through food. If you're an average trainer who eats reasonably well, adding 1,000 calories of liquid carbohydrate on top of your normal diet will add body fat, not just muscle. Many people buy mass gainers because they seem like a shortcut, then wonder why they're gaining fat. A regular whey protein shake with added oats and milk is often a more controllable and cheaper alternative.

Amazon ratings are a particularly unreliable signal in this category. Taste drives most star ratings on mass gainers — a product that mixes easily and tastes like a milkshake will collect five-star reviews even if its formulation is mediocre. Our scoring looks at ingredient quality and value for money separately from consumer satisfaction, and the gap is often significant. Don't mistake popularity for quality.

Another common error is ignoring serving yield. The 6kg tub of Critical Mass Professional from Applied Nutrition (74/100, £52.95) looks expensive next to the 2.4kg version (80/100, £40), but when you factor in 40 servings versus 16, the larger tub costs less per serving. Run the maths before you buy, particularly on the bigger tubs where the per-serving cost tends to drop considerably.

Types and Forms Explained

Every mass gainer in our dataset comes in powder form — 12 products labelled explicitly as "powder" and a further 6 capitalised as "Powder," with no meaningful difference between the two designations. Unlike some supplement categories, mass gainers simply don't exist in capsule or liquid form at meaningful calorie loads. You cannot fit 600 calories into a capsule. What does vary significantly, though, is the formulation philosophy within that powder format.

Lean mass gainers sit at one end of the spectrum. These typically deliver 400–600 calories per serving with a higher protein-to-carbohydrate ratio, and they use cleaner carbohydrate sources. Applied Nutrition's Critical Mass range falls here. They're suitable for people who want to gain mass without excessive fat, or those who are sensitive to the blood sugar swings from maltodextrin-heavy products. The trade-off is that you may need to consume more than one serving per day to hit a meaningful caloric surplus.

High-calorie mass gainers — often 700–1,200 calories per serving — are designed for people who struggle to eat enough no matter what. Optimum Nutrition's Serious Mass (72/100, £52.95) sits in this camp. These formulas typically rely more heavily on maltodextrin to hit those calorie targets, and they're best used strategically: one shake post-workout or between meals, not as a meal replacement. If your goal is pure scale weight gain and you're not gaining on anything else, this type may be appropriate.

Some products sit in a middle ground, blending a moderate calorie count with a more diverse ingredient list — added creatine, glutamine, or BCAAs. These aren't necessarily better; often the extra ingredients are included at sub-effective doses purely as marketing. Check whether the added creatine, for example, actually reaches the 3–5g effective daily dose, or whether it's a token 500mg added to justify a premium price.

What to Expect to Pay

At the lower end of the market — roughly £21 to £35 — you're typically looking at high-maltodextrin formulas with lower protein content and minimal quality control. These can work for gaining scale weight, but you're unlikely to be getting the protein quality or carbohydrate profile that supports lean mass specifically. This price range is appropriate if you're a true beginner who simply needs calories and isn't yet concerned with optimising macronutrient quality.

The £35 to £55 range is where most of the credible products sit, and it represents the best value territory in this category. The Critical Mass Professional Lean Mass Gainer in the 2.4kg Banana format (80/100, £40) is the top-rated product across all 25 we analysed and also the best value for money, scoring 80/100 on value. At £40 for 16 servings, it's not the cheapest per serving, but the formulation quality justifies the price. Bulk's Informed Mass (77/100, £45) is the next strongest option in this bracket.

Above £55, gains in formulation quality become marginal. Optimum Nutrition's Serious Mass at £52.95 scored 72/100 — decent, but not exceptional given the brand premium. The Critical Mass 6kg Vanilla tub at £62.76 scored 71/100, which is below the category average despite the higher price. At this level, you're often paying for brand reputation or larger pack sizes, not meaningfully better ingredients.

As a general guide: budget £40–50 for a quality mass gainer that will last two to three weeks at one daily serving. Anything below £30 warrants close scrutiny of the label. Anything above £60 needs a compelling reason — usually a significantly larger tub size with a better per-serving cost, not a premium formulation.