But the famously slender Roberts admits she piled on the pounds during shooting for the Italian segment of the story, where her character munches her way through an endless array of dishes during a quest for nourishment.
"We went to the place where Liz had pizza, got there at eight in the morning and proceeded to shoot, and I started my day with eight entire slices of pizza in 45 minutes," Roberts told journalists at a publicity event in Napa Valley.
"The deliciousness of something wears a tiny bit after piece seven. I would eat an entire slice in a take. I don't know why I thought that was a good idea," Roberts said, revealing she gained 11 pounds during the Italian filming.
"But I loved every pound, and everyone said it was going to drop right off in India, and that didn't happen. I didn't get that memo."
Twenty years after rocketing to global superstardom in 1990's smash hit "Pretty Woman," Roberts, 42, remains one of Hollywood's elite acting talents, a star who regularly ranks among the world's highest paid celebrities and is in complete control of her career.
Roberts said she was drawn to "Eat Pray Love," which is released in North American on August 13, soon after Gilbert's memoir was published in 2006.
"I read it before it became so widely popular, and I thought it was so terrific 30 pages into it, that I went on Amazon.com and sent one to my best friend in Chicago, and said, 'Let's read this,'" Roberts revealed.
Roberts, who has been happily married to cameraman Daniel Moder since 2002, with whom she has three children, said she could relate to Gilbert's quest for happiness even if she had allowed her life to unfold at its own pace.
Asked if she had tried to evolve her life like Gilbert, Roberts replied: "Not in the urgent pursuit way that she's experiencing it, but I definitely knew that my life would continue to evolve until I found that place to occupy and live in, which is the home I have now.
"But I relate to her search and pursuit, and it was definitely great to have a fulfilled sense of my own life."
Although Roberts met Gilbert during filming in Rome, the actress said she was careful not to allow that to shape her performance in the film, which is directed by Ryan Murphy, best known as the creator of cult television series "Nip/Tuck" and the phenomenally successful Fox network show "Glee."
"I met her in Rome. I didn't want to meet her before that, because I knew that she and Ryan [Murphy] were in close communication, and obviously, in this endeavor, the first step I took was to put my complete and total trust in Ryan," Roberts recalled.
"I knew that his paper interpretation of her that he gave me was all I would need, and I was also worried about falling too much in love with her, so that I would try to be her, as opposed to interpreting her as an actor."
Roberts is backed by an impressive stable of co-stars in "Eat Pray Love" including James Franco, Richard Jenkins, Billy Crudup, Viola Davis and Spanish Oscar-winner Javier Bardem.
Roberts admits that she was initially nervous about working with Bardem, who plays her love interest in the film, following the Spanish heart-throb's chilling Oscar-winning performance in 2007's "No Country for Old Men." Her fears proved to be ill-founded.
"I was a little terrified to be around him after 'No Country For Old Men.' I said to him near the end of filming, 'You know, I thought you'd be so intense and weird, and I'd have to be like, handling you, but you're just so sweet and funny, and it's just so easy!' And he said, 'I'm not like that normally. I just wanted to try it once to see how it worked!'
Bardem's energy ultimately proved to be infectious, Roberts recalled.
"It was like deciding to get a puppy. You have everything in your house worked out, and then the puppy comes in, and you're like, I'm way too tired to have a puppy," she said.
"Javier came in with all this gusto and enthusiasm and he wanted to read the scenes and go over some stuff. And then you realize no, this is getting good, let's have lunch, let's go over scenes, let's look over the stuff! His excitement was so contagious."
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