KFC fans have claimed they've been left feeling "sick" after a Channel 4 documentary revealed how its world-famous gravy is made.

Inside KFC at Christmas aired on TV screens across the UK earlier this week giving viewers an inside look into how the fast food chain really operates.

A segment of the show, which reveals the secrets of the well-loved chain, revealed how staff prepare its well-known and loved gravy pots.

Team member Anne Walker was seen using leftover juices from the bottom of the restaurant's chicken fryers.

Barrhead News: Picture: CHANNEL 4/INSIDE KFC AT CHRISTMASPicture: CHANNEL 4/INSIDE KFC AT CHRISTMAS

In the documentary, she says: "You get the crackling and then three and a half litres of cold water - two scoops of crackling.

"You get your juices off your chicken and then you get your magic ingredient."

Ms Walker is then seen using a foil bag, which contains the remaining ingredients for the gravy.

As she adds the mix, she says: "Pour that in there, whisk it up so it’s nice and smooth and all the bits are all mixed up. Voila. Then we just pop it in the microwave."

'It's made be feel physically sick'

But taking to social media after watching the show, dozens reacted with some saying they had been left feeling "physically sick."

The show aired earlier this week but is available on Channel 4's website and through catch-up TV.