Apple has admitted that chief executive Steve Jobs is skipping Tuesday's Macworld keynote for health-related reasons, after initially pointing to other reasons for his absence.

(Credit: James Martin/CNET News)

Throughout 2008 Apple was plagued with rumours about Jobs's health, but steadfastly refused to acknowledge that anything was behind concerns over what many believed was substantial weight loss suffered by the iconic Apple founder.

Apple surprised onlookers in December with the news that Jobs would be skipping his much-anticipated Macworld keynote, but said the reason was that Apple had decided not to invest in a Macworld keynote because it would be the company's last year at the show.

However, Apple's board of directors put out a statement on Monday acknowledging Jobs would need some time to recuperate from what he called a "hormonal imbalance". In a letter to employees yesterday in the US, Jobs said he had decided a few weeks ago that getting to the bottom of his mysterious weight loss was his biggest priority, and doctors had determined that the imbalance was 'robbing' his body of the ability to be healthy.

Jobs will continue as chief executive while he is regaining weight through what he called a "simple and straightforward" remedy, which is expected to last until late spring, he said in the letter. "I have given more than my all to Apple for the past 11 years now. I will be the first one to step up and tell our board of directors if I can no longer continue to fulfil my duties as Apple's CEO," he said.

Apple's stock has rallied on the news. In the first 15 minutes of trading, the stock was up around four per cent, which could be an indication that since Jobs's health situation is not as dire as some reports had indicated, investors are confident he will continue as chief executive.