Starters Guide to Optimum Nutrition Serious Mass Before we go in to the discussion about serious mass, let us have a brief introduction about optimum nutrition. Optimum nutrition is a famous name in the market, when we talk about weight gain protein supplements. It is one of the most trusted brands in the market. It is the creator of many weight gain supplements, and among them is serious mass. As the name suggests, serious mass means serious calories, it is quite high in calories and it a perfect protein powder if you are seriously considering to gain some muscle mass. It stands true to its name; you will surely end up gaining a few pounds after using it for a while. The mission statement of optimum nutrition is to produce distinctive, affordable and premiumquality products, while keeping in mind the needs of the customers and to meet up with the demands of the market with innovative products. Before we get into any further discussion, let us get the basic facts right about serious mass.