How can actors explain essential increase of muscles in short period of time?

Steroids are definitively administrated by different actors. You can observe dramatical changes in actors’ physique in short time. For example, a certain actor has played a role in a film, being quite thin, then, after short period of time he plays a role with increased muscle mass. How may actors enhance their muscle mass in short period of time? The answer is obvious. They use anabolic steroids. But actors deny that they administrate performance-enhancing drugs.
Jason Momoa in “Conan the Barbarian”, Chris Hemsworth in “Thor” and Chris Evans in “Captain America: The First Avenger” enhanced their muscles essentially to play certain roles. Undoubtedly, this aspect led to questions about steroid use. But the actors refused to answer the questions linked with administration of performance-enhancing drugs.
It is known that Jason Momoa enhanced his muscle mass by 30 pounds to play Conan. An actress, Rose McGowan, that also played in “Conan the Barabarian” pointed out that Momoa reached that results not because of steroids. Jason Momoa mentioned that he wanted to correspond to a Frank Frazzeta painting without intake of steroids. It would be ideally, according to this actor. But he noticed that our world and life were not ideal. Momao confirmed that he had trained hardly. Moreover, he followed a strict diet. He ate broccoli, peanut butter, yams and chicken breast continually.
As for Chris Hemsworth, this actor increased his muscle mass by 20 pounds in order to play Thor. The actor claimed that he had eaten a lot. He noted that he had eaten and he seemed as if he were busy with an important thing. He claimed that it had been very difficult to eat, when he was not hungry. Furthermore, Chris Hemsworth had to eat large amounts of food. According to his words, it was too tiring.
It is interesting to mention that Hemsworth never lifted weights before playing his role in “Thor”. Couldn’t you find this aspect unreal without administration of steroids? Nevertheless, he confirmed that he hadn’t administrated anabolic steroids.
Chris Evens also enhanced muscle mass significantly in order to play Steve Rogers in the film “Captain America: The First Avenger”. He confirmed that he had increased muscles due to trainings and a strict diet.