Kris Jenner is on a revenge diet.

The Kardashian family matriarch has reportedly embarked on a strict new diet in a bid to help her get into the best shape of her life, as she is fed up of being compared to glamorous ex-partner Caitlyn Jenner, who was known as Bruce Jenner until she underwent gender transition earlier this year.

A source close to the 59-year-old star said: ''All the jokes about how Caitlyn is hotter than Kris hit her hard. Normally Kris is pretty thick-skinned, but she's hit a new low.

''Kris hates how badly she's been portrayed since Caitlyn's big reveal.''

The 'Keeping Up with the Kardashians' star is said to be sticking to a 1,000-calorie-a-day diet with no-solids to help her reach her goal weight.

The insider told OK! magazine: ''She's already lost 14 pounds by living off protein shakes, and she's determined to stick with it until she loses another 20, which is insane.''

Kris' children, including youngest daughter Kylie Jenner, 17, are concerned she still isn't coping with Caitlyn's transition.

The source added: ''Her kids can see that she's hurting, but there's no talking her out of it. Kris wants to feel hot again, and she's convinced losing a bunch of weight is the only thing that will do it.

''She wants to share clothes with Kylie.''