If you want to to bulk up fast without getting fat then you have to understand that eating way more calories than your maintenance won’t make you gain lean muscle mass faster but actually it will make you fatter faster. Here are some strategies which are proven to help a person bulk up fast while minimising fat gain but remember when you eat a surplus of calories some fat gain is inevitable.
Eat in a caloric surplus of around 10–15 percent to your maintainance calories, this is all that is needed to gain muscle at an optimal rate.
Eat minimum of 2.5 grams of protein per kg of body weight, there was a study conducted on female physique competitors which concluded that females who ate this much protein gained lean muscle mass on a calorie deficit.
Perform some form of cardio 3 to 4 times per week, many people make the mistake of totally avoiding cardio while trying to gain muscle which is not a smart strategy. Doing some light cardio three to four times week enhances the cardiovascular fitness and helps in shedding fat.