When one has a fast metabolism, consumes fewer calories a day, or wants to gain muscle mass and size, one requires lots of nutrients that a food diet may not fulfil- opt for Steadfast Nutrition’s Power Massive, a mass gainer loaded with calories, carbohydrates, protein, essential vitamins, and minerals, which help you bulk up and gain muscle mass and weight. The simple and complex carbohydrates and slow and fast-releasing proteins promote muscle synthesis and repair, and provide instant energy, refilling lost glycogen stores.