Optimum Nutrition Serious Mass 12Lbs

Optimum Nutrition Serious Mass 12lb — 1,250 Calories and 50g Protein Per Serve

Serious Mass is the highest-calorie gainer Optimum Nutrition makes, and the 12lb tub is the size that keeps you in it. Each full serve delivers over 1,250 calories, 50g of protein from a whey, casein and egg blend, and 250g+ of carbohydrate, plus creatine, glutamine and 25 vitamins and minerals. In stock at TopDog Nutrition.

Who a Gainer Is Actually For

Gaining weight is a calorie surplus problem, and for some people it's genuinely hard. If you have a fast metabolism, a physical job, or you simply lose your appetite before you hit your target, eating 4,000 calories a day of whole food is a full-time job. Chewing becomes the bottleneck.

That's the problem Serious Mass solves. Over 1,250 calories in a drink, taken between meals, closes a gap that food alone was never going to close. It's not a replacement for eating — it's what goes on top when eating isn't enough.

If you're not struggling to eat, you don't need this. A regular whey protein plus more food is cheaper and easier to control.

The Protein Blend — Whey, Casein and Egg

50g per serve, and deliberately from three sources rather than one:

• Whey digests fast, spiking amino acids in the bloodstream quickly.
• Casein forms a gel in the stomach and releases over several hours, extending amino acid availability well past the shake.
• Egg protein sits between the two on digestion speed and brings a different amino acid profile again.

The result is a longer amino acid curve than any single source produces. For a product you're often taking between meals, that sustained release matters more than a fast spike.

250g+ Carbohydrate — Why So Much

Carbohydrate does two things here. It supplies the bulk of the calories, and it replenishes muscle glycogen — the stored fuel that heavy training depletes. Training hard in a surplus without enough carbohydrate means training on empty.

There's also an insulin effect: carbohydrate raises insulin, which drives amino acid uptake into muscle. That's why gainers pair large carbohydrate doses with protein rather than selling protein alone.

Creatine, Glutamine and 25 Micronutrients

Serious Mass includes creatine, the most researched performance supplement there is, supporting ATP regeneration for strength and power output. Glutamine supports recovery and gut function — relevant when you're pushing a large volume of food through your system daily.

The 25 vitamins and minerals matter more than they might seem. Eating in a large surplus using calorie-dense foods can leave micronutrient gaps, and the fortification covers that ground.

Why the 12lb Size

At a full serve a day, a 12lb tub gives you around 16 serves. That's a fortnight or so — which tells you something about how quickly gainers get consumed.

The 12lb is the better buy per serve than the 6lb, and if you're committed to a bulk you'll be reordering either way. The 6lb makes sense for trying it first or for half-serves.

Directions

Blend 2 scoops with 700ml of water — a blender is genuinely better here, as this is a lot of powder for a shaker. Take between meals or after training.

Start with half a serve. 1,250 calories in one go is a lot for a digestive system that isn't used to it, and going in at full dose on day one usually means feeling bloated and skipping the next. Build up over one to two weeks.

You can add fruit, peanut butter or oats to push the calories higher, or mix with milk instead of water.

Allergens

Contains milk, egg and soy. Check the label for flavour-specific allergen information.

Frequently Asked Questions

Will this make me fat?

It'll make you gain weight — that's the point. How much of that is muscle versus fat depends on your training and how aggressive the surplus is. 1,250 calories on top of an already adequate diet is a big surplus. If you're gaining faster than roughly 0.25–0.5kg a week, halve the serve.

Serious Mass or Pro Gainer?

Pro Gainer runs a higher protein-to-carbohydrate ratio at fewer total calories — 60g protein and a more controlled carb load. Serious Mass is the maximum-calorie option. Struggling to gain at all: Serious Mass. Want to gain more slowly and leaner: Pro Gainer.

Can I take half a serve?

Yes, and most people should start there. Half gives around 625 calories and 25g protein, which is a substantial addition on its own.

How many serves in a 12lb tub?

Around 16 full serves, or 32 at half.

Do I still need creatine separately?

Serious Mass contains creatine but not necessarily a full 5g daily dose. If creatine is a priority, a dedicated micronised creatine gives you control over the dose.