The pair ' who tied the knot at the luxury Aman-i-Khas resort in Rajasthan, India, last month ' are determined to get fit and feel healthier, and so have cut out all wheat and dairy until the end of this year.
A friend of the couple said: 'Katy and Russell are taking care of themselves and are on a mission to get fit. As well as cutting out wheat and diary, they're on a diet of raw vegetables, tofu and pulses.
As well as their special diet, the British comedian ' who is vegetarian - and his pop star wife also appear to have picked up some health tips during their recent stay in India.
The source explained to the Daily Star newspaper: 'They're both drinking loads of pineapple juice and are obsessed with Indian green tea which is full of anti-toxins and great for weight loss.'
However Katy's and Russell's new health kick may not last until the New Year as the pair are said to be planning a fun filled family Christmas in London.
The insider revealed: 'Katy and Russell are trying to get their families together for their first Christmas as husband and wife. Katy thinks a white Christmas in London would be romantic.
'They are hoping to have a proper knees-up with the whole of Russell's family. Katy's mum and dad are hoping to come to London as well.'
The 26-year-old star, who has lost 50lbs since her appearance on last year's 'Dancing With The Stars,' said criticism of her size when she was younger ruined her self esteem and made her 'hate' herself.
Kelly ' the daughter of Sharon and Ozzy Osbourne - said: ' understand that being judged by others comes with the territory, but it broke my heart and ruined my self esteem.
't sets you up to hate yourself in a huge way. I was so angry about the things people said about me. I truly believe it's the main reason I turned to Vicodin and ended up in rehab three times. I just hated myself.'
Kelly - who split from fiance Luke Worrall earlier this year amid rumours he had cheated on her ' admitted she had once been an emotional eater who binged on calorific snacks and only managed to change her ways thanks to the guidance of her 'Dancing with the Stars' partner Louis van Amstel.
She told Shape magazine: ' used to eat chips and cookies and drink soda all day long. I had to start making better choices.
' indulge with pizza and cheese - I love Brie - and have cookies sometimes. But now, when I'm full I stop eating! It may have taken me 26 years to figure it out, but I've finally learned how to do it right.'
'Louis made me eat turkey burgers and salads. Then I started losing weight and realised, 'Oh, it's true what they say: Diet and exercise really work!' '