Charlize Theron is well aware she is no longer in her twenties, and she feels it. In Variety's latest cover story, the 41-year-old South African beauty talks about her fluctuating weight in preparation for her two films, "Tully" and "Atomic Blonde."

Gaining weight

The actress is not new to the demand of putting on weight for a role. It can be recalled that her body transformation for the Oscar-winning film "Monster" was one of her defining moments in the industry.

In this movie, she got everyone talking when she won an Oscar for her portrayal of serial killer Aileen Wuornos.

Theron gained over 30 lbs for the role by eating donuts and potato chips.

When "Monster" was filmed, Theron was much younger and in her twenties. At the time, the fluctuations in weight was not an issue for her or her body. In the comedy film "Tully," she plays a mother of three, which is a more mature role. She has commented in the past that for her career, she tries to transform herself towards the characters.

This time, however, she really felt it in her health. The actress described the experience brutal in every sense. According to her, the sugar put her in a massive depression and she was sick. On top of that, she was frustrated because she couldn't lose the weight.

When she called her doctor for help because she thought she was dying, he told her to calm down.

She isn't dying, she's 41. Case in point, she admits it is more difficult now that she's in her forties.

Shaping up

As for her new movie "Atomic Blonde" where she plays a bisexual killer queen spy, Theron had to push her body to the limit to learn all the tough moves. The training was so rigorous she ended up cracking her teeth from clenching her jaw too hard.

Before filming in Budapest, she had to undergo surgery- cut one of the teeth out and root canal. She recalled this experience as tough. Further, she describes how difficult it was to be in her best fighting shape. Her dental surgery took quite a while to heal and recover. She had to make necessary adjustments to ensure she's back in shape the soonest possible.

To be effective in playing the role of a spy with immense fighting skills, Theron had to do heavy training and learned a number of martial arts techniques for two and a half months. Film director David Leitch took it even further by revamping the fight sequences and making them more complex.

Theron is well-known for her realistic portrayal of characters. According to her, she loves her job as an actor, especially the transforming and becoming aspect of it until it the character goes beyond her. True enough, her commitment to her craft, her job, and her characters continue to pay off.