LOS ANGELES (NEW YORK TIMES) • Once, while at a fitting for a television commercial, mixed martial arts fighter Ronda Rousey received unwelcome feedback.

She had been planning to lose a few kilogrammes before filming, "but because somebody said something really rude to me, I came into the shoot purposely way heavier", she recalled on a recent afternoon at her home in the beachside neighbourhood of Venice.

Did they dare question her?

"No," Rousey said with a grin, "and the campaign ended up being amazing, even though I was heavier just to make a point." (She declined to say the advertisement was for which company, but noted that her breasts are bigger in it than in any other commercial she has done.)

"I swear to God," she said, shaking her head, "if anyone calls me fat one more time in my life, I'm going to kill them."

At one time, up-and-coming Hollywood personalities did not say such things. But Rousey, 28, a tight coil of muscle and moxie, is helping slake the entertainment industry's sudden thirst for female feistiness. The first American woman to win an Olympic medal (bronze) in judo, she turned to mixed martial arts in need of a new challenge and to give up the drinking, smoking and pill-popping that seduced her after her success in Beijing in 2008.

She trained for the Ultimate Fighting Championship even though its president Dana White said he would never let a woman into the league.

Rousey's prowess changed that - there are more than 50 women now in the championship - and since her 2013 debut, she has been undefeated in her weight class. Her signature move, the arm bar (which she learnt from her mother, former judo world champion AnnMaria De Mars), is designed to hyperextend her adversary's elbow, leave her in a cast and, ideally, produce another victory.

Rousey is sweet yet vicious, able to break an arm one day and gyrate topless for a denim advertising campaign the next.

"I found a contrast between what I've seen her do in the ring and this hippie girl who lives in Venice and loves music and is creative," said Peter Berg, who is directing Rousey in the film Mile 22 with Mark Wahlberg. She plays a CIA field operative in Indonesia desperate to return home to her daughter, a meatier role than Rousey's small part in Entourage this past summer.

Her next major film project is an adaptation of My Fight/Your Fight, a memoir she wrote with her eldest sister, Maria Burns Ortiz, a former sports journalist. Rousey will play herself for the bulk of the movie.

When she was eight, her father, suffering from a back injury that had become debilitating, killed himself.

Fighting gave her a focus through her teens, but struggling with weight limits for judo tournaments fostered a fraught relationship with food and, for a time, bulimia.

In 2012, she posed nude on the cover of ESPN magazine. She has been in similarly sultry shoots, in part, she said, to embrace the body that used to embarrass her.

She said: "When women say that going on publications directed at men is somehow demeaning, I don't think that's true.

"I think that's one really effective way to change the societal standard women are held to."