How Actors Bulk Up So Quickly For Movie Roles

Probably one of the craziest weight gains for movies is when Christian Bale bulked 60 pounds for Batman after the role in Machinist.

I'd say the key principles in gaining weight fast (or gaining muscle in general) are:

1. Simple heavy compound lifts at the gym like Squat, Deadlift and military/bench presses. Small reps <5 and high sets >5. Increasing the frequency of training session to be as often as possible, right after recovered.

2. Eating a lot of high quality calories from real foods with supplementation if needed. I think is the hardest part. It is difficult to eat enough good food with optimal macro-nutrient balance, say 20/30/50 protein/fats/carbs or whatever personally works for you. Also, you need to get good amount of vitamins and minerals from the foods so just bulking burgers and protein shakes won't be enough.

3. Sleep and conditioning are super important to make sure you can recover fast enough to have enough training session per week.

I think these principles are simple and applicable to any person wanting to gain muscle. Naturally, you can tweak and optimize everything as much as possible but I'd say 80% of the times people are trying to gain mucsle and fail is because they can't get these principles right simultaneously and maintain them.