Hollywood actor Sally Field had to gain 25 pounds for Steven Spielberg’s “Lincoln.” Speaking on “The Tonight Show with Jay Leno” Thursday, Ms. Field said that the process she used to put on pounds was “just disgusting.”

“It was hard, it was very hard,” Ms. Field said. “It wasn’t as much fun as you would think.”

The seasoned actor will play Mary Todd Lincoln, the wife of Abraham Lincoln (who is played by Oscar-winning actor Daniel Day Lewis).

“First of all, it was horrifying because I’m of a certain age and I kept thinking, ‘If I don’t do it right I will drop dead halfway through this and someone else will get the role!” Ms. Field said.

To lose 25 pounds for the role, the veteran actor modified her diet.

“I tried to do it healthy, which I understand there isn’t any way to do it healthy,” Ms. Field noted. “I ate brown rice and these protein drinks made out of stuff called pro-Gain … Oh God, it was just disgusting. I never had a fun meal, basically. It just was discipline.”

Reviews of Mr. Spielberg’s “Lincoln” are mostly positive. Lauren Moraski of CBS News compiled a number of review excerpts. Check out some of them below:

“The portrait of Lincoln transcends conventional judgments; it’s a complete creation, perfect on its own terms,” writes Joe Morgenstern of The Wall Street Journal.

“There is nothing bravura or overly emotional about Spielberg’s direction here, but the impeccable filmmaking is no less impressive for being quiet and to the point,” writes Kenneth Turan of The Los Angeles Times.

“In all, there’s too much material, too little revelation and almost nothing of Spielberg’s reliable cinematic flair,” writes Rex Reed of The New York Observer.

Regardless of the review, Ms. Field told Leno that she’s just happy to be able to eat what she wants again.

“I stopped eating, and I’m hungry now,” Ms. Field remarked. “It took me about six months to gain it, and about a year to lose it. I began to work out like a mad fiend. I had two trainers. I really worked out hard 4 times a week.”

Not only was the process of losing wait for her big role “disgusting” but it eventually led to some serious wear and tear on her body.

“I eventually had to have knee surgery. My little frame couldn’t hold this amount of weight,” Ms. Field revealed.

Bloomberg News reports that “Lincoln” is expected to generate $94 million in North American ticket sales. The news outlet estimates that DreamWorks Studios, Participant Media and Twentieth Century Fox spent somewhere between $97 million and $130 million making and marketing the film which leaves very little room, if any, for profit.

“Lincoln’ needs to catch on internationally to be profitable,” Phil Contrino, vice president and chief analyst at BoxOffice.com, told Bloomberg News. “Ninety-four million domestically would be seen as successful, but success at home is not enough these days. I’m sure they spent a lot of money marketing it.”

“Lincoln” was released on November 8th in 11 theaters. The film will be released in 1,500 theaters the following weekend.