Sandi Toksvig is to leave The Great British Bake Off after three series.
In a statement, the presenter said she was leaving in order to focus on other work commitments.
"As my waistline will testify, Bake Off is an all-consuming show," , adding that hosting had been one of the "great pleasures" of her life.
Toksvig and Noel Fielding originally took over presenting duties when the programme moved to Channel 4.
Prior to that, the show aired on the BBC and was fronted by Mel Giedroyc and Sue Perkins, known as Mel and Sue.
She will still appear on next edition of The Great Celebrity Bake Off for Stand Up To Cancer, broadcast in the Spring.
Sandi Toksvig's statement in full:
"When stepping down from a job it is quite common for people to say they are doing so in order to spend more time with their family. Unusually I am departing from the Great British Bake Off so I can spend more time with my other work.
"As my waistline will testify, Bake Off is an all-consuming show. Spending time with Prue, Paul and Noel has been one of the great pleasures of my life. These are friendships which I know will continue beyond the confines of television.
"Bake Off is a wonderful programme which has already proved it can happily withstand a change of hosting personnel. The reason for that, of course, is that the true stars of the show are the bakers themselves. I wish everyone well."
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