When one “bulks” this is of course to put on more weight. The objective is clean weight (muscle) and a limited amount of fat. This is called a “lean bulk. The eating is clean with a good amount of carbs and protein with a minimal amount of fats. Maybe you are in a position where you know you are eating a lot of food and lifting hard but seem to be gaining more fat than you want. Observing not only the macros breakdown but also the foods you are eating and cardio (yes cardio) you are performing plays a huge role. A common macros breakdown of the total calories consumed by a person bulking lean should be around 40/40/20. This means 40% of calories are carb calories, 40% are protein calories, and 20% are fat calories. And remember, do not look down on cardio.
When a person is bulking, remember the objective when a person is bulking correctly: put on CLEAN weight. Dirty bulking provides all the downfalls of adding unwanted fat and covers up whatever muscle has been gained. Sound like you? When bulking, you are consuming extra calories. These calories are composed of course of carbs and fats. By implementing light to moderate cardio sessions (getting the heart rate to around 50%-70% of MHR), this will not only help with burning unwanted fat that may have been gained but it allows the body to be open to consuming more calories to continue to bulk up cleanly.
Nutrition is important as stated all the way around. Before, during and after a workout. Carbs and protein are vital for muscle growth, so making sure they are in your body always will only pay off in the end.