(CNN) Anthony Joshua has denied claims he suffered a panic attack ahead of his shock defeat by Andy Ruiz Jr. in New York on Saturday.

In a video posted on the heavyweight boxer's YouTube channel, Joshua also denied that he had experienced food poisoning, instead accepting responsibility himself for the loss.

Joshua entered the fight at Madison Square Garden as heavy favorite, but fell to his first defeat in 23 professional fights when he was knocked down by Ruiz in the seventh round.

"It was an amazing night, an amazing night altogether," said Joshua.