When choosing your muscle gain level, you’ll need to decide how much weight you’d like to gain each week and how much body fat you’re comfortable putting on.
The more aggressive the muscle gain setting, the more food you’ll be eating. Clearly this will enable you to put on more muscle, but the bad news is that it also opens the door for more fat gain. There’s a limit to the amount of muscle you can build each week, and the excess calories you don’t burn off or use to build and remodel muscle will be stored as fat. Even with the largest calorie surplus and best training program, you can’t force feed muscle.
With this in mind, if you’re concerned about staying lean, you should choose a slow or moderate muscle gain option on the slider.
But if you’re a “hardgainer" or athlete on an extended off-season wanting to get big and strong at all costs, then choosing a more aggressive muscle gain setting is your best course of action.