The comedy series in the vein of 'Curb Your Enthusiasm' stars Alley as an overweight actress trying to get work in Hollywood, obsessed with her weight and appearance.
It will be largely improvised and partly autobiographical, and feature guest stars including John Travolta and former 'Baywatch' star Carmen Electra. The series will run on FX in UK in the autumn.
'Fat Actress' has garnered a huge amount of publicity in the US because it examines the contradiction of a nation that is obsessed with losing weight and at the same time promotes the idea of self-acceptance. It has been well received by critics.
The Showtime deal will also gives FX exclusive UK rights to two other unnamed drama series, yet to air in the US.
The network has already had success with another Showtime programme 'Huff'. It stars Hank Azaria, known for his work as a voice actor on 'The Simpsons', playing a troubled psychiatrist called Craig Huffstodt.
Jason Thorp, vice-president of broadcast and marketing at Fox International Channels UK, said: "This is major deal for us and these great, new, quality shows will help continue to establish FX289 as one of the key entertainment brands on multichannel television."
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