Megan Fox struggles to gain weight

The 25-year-old, who is famous for her role in the movie `Transformers`, tries hard to shed her skinny image, reported Us magazine.

"Believe it or not she has this really fast metabolism. So her training is all about body toning and sculpting. With her it`s really about she`s eating enough of the right things. `Oh she must be anorexic` but she`s far from that!

"She gets frustrated at times because she`s like `I need to put on weight.` So she actually weight-trains to keep on that lean muscle tissue," said Pasternak.

Because of her really thin frame she was asked to gain weight for the `Transformers` role.

"I`d lost a lot of weight and got really scrawny but I was told I had to put on a size for Transformers because Michael Bay, the director doesn`t like skinny girls," said Fox.