Sydney (AFP) - Dethroned UFC world champion Ronda Rousey vowed on Monday she would be back after "a little bit of time" following her stunning knockout defeat to Holly Holm in their title fight in Melbourne.

Holm pulled off one of the biggest upsets in the Ultimate Fighting Championship when she knocked out previously unbeaten Rousey in the second round to claim the world bantamweight title on Sunday.

Rousey, tagged the world's most feared female prizefighter, was hospitalised after Holm sent her crashing to the canvas in the second round of their bout with a savage kick to her jaw.

But the US cult figure assured her supporters she has no serious health concerns and would be back in the octagon before long.

"I just wanted to thank everyone for the love and support," Rousey said in a statement posted on Instagram. "I appreciate the concerns about my health but I'm fine.

"As I had mentioned before, I'm going to take a little bit of time but I'll be back."

There were reports after the fight of a re-match between the newly-crowned champion and Rousey.

Rousey's nutritionist and conditioning expert Mike Dolce said he expected her to rebound after her unexpected defeat.

"She will be back, absolutely, she is an amazing athlete," he told reporters in Sydney.

"Ronda has lost before, she lost at the Olympic Games and I think that was a great test for her and look at how she came back, she came back a multi-time world champion.

"So I will be expecting the same type of rebound after this."

Rousey claimed a bronze medal in judo at the 2008 Beijing Olympics before fighting her way to the top of the UFC and Dolce said she would draw on that experience ahead of a probable re-match against Holm.

"We go back to the gym, we go back to the basics, we go back to what made her a champion in the first place which is just hard work, sacrifice, dedication and focus on being the best in the world," he said.

"Last night was unfortunate but it doesn't change the overall goal which is being the best athlete on the planet. We knew going in that Holly would be a tough test and she certainly was," Dolce added.

"Holly is a great champion and you can't take that away from her."

Holm had Rousey staggering in the second round with some crunching left hooks, before finishing her off with a left-foot kick that landed flush under the champion's jaw.