Big news for hardgainers and serious athletes: Optimum Nutrition's iconic Serious Mass is now available in the massive 12LB size — and you can get it exclusively online at Fuelsupplements.com right now, with in-store availability arriving in early April next week.
If you've been stacking tubs to hit your calorie goals, the 12LB bag is the upgrade you've been waiting for. More servings, more value, and the same trusted formula that's made Serious Mass one of the best-selling weight gainers in the world.
Why Serious Mass? The Science of Calorie & Protein Surplus
Building muscle isn't just about lifting heavy — it's about fueling your body with enough calories and protein to actually grow. Research consistently shows that a caloric surplus combined with adequate protein intake is essential for hypertrophy and lean mass gains.
👉 Learn more: How Much Protein Do You Need to Build Muscle? (Healthline)
Each serving of ON Serious Mass delivers:
- ✅ 1,250 calories per serving
- ✅ 50g of blended protein (Whey Protein Concentrate)
- ✅ 254g of carbohydrates from Maltodextrin
- ✅ Available in Chocolate and Vanilla
Whether you're a hardgainer struggling to eat enough, or an athlete in a dedicated bulk phase, Serious Mass is engineered to close the gap between where you are and where you want to be.
Choose Your Size
We now carry both sizes so you can stock up the way that works for you:
Shop the Full Optimum Nutrition Lineup
Serious Mass is just one of the many premium products from Optimum Nutrition available at Fuelsupplements.com. Browse the complete collection to find the right supplement stack for your goals.
👉 Shop All Optimum Nutrition Products →
Build Your Stack: Protein + Mass Gainer
Serious Mass works best as part of a complete nutrition strategy. If you're newer to supplementation or want to dial in your protein intake on training days when you don't need the full calorie load, pairing it with a quality protein powder is a smart move. Not sure where to start? Our in-depth guide breaks it all down:
👉 Fuel Your Fitness Journey with Protein Powder →
And for a head-to-head look at another top mass gainer on the market, check out our review:
- 📖 Dymatize Super Mass Gainer Review — How does it stack up against the competition?
Get It Before It Hits Stores
The ON Serious Mass 12LB is available exclusively online at Fuelsupplements.com right now. In-store availability begins next week April 6th — so if you want to be first, order online today.