50-year old Sanjay Dutt has been shooting with 20-something Kangana Ranaut. And if they were looking super-compatible in spite of Kangana being half the age of Dutt, it's all because of Dutt's special ketosis-based diet.

Says a source close to Dutt, "Sanjay went on this special diet in June. It required him to take lots and lots of fattie food and no carbohydrates at all. In fact carbs would've been potentially lethal for this diet. In no time Sanjay started losing weight. And that too without Sanju having to give up his favourite food."

Today, Dutt is looking trimmer than he did ten years ago. And when he shot with Kangana last week, the camera made them look compatible.

Dutt plays an assassin out to get his victim with a sniper rifle in Knock Out. Kangana Ranaut has always had a fascination for assassin heroes. She began her career with Gangster where her assassin-hero was Shiney Ahuja.

Now in Mani Shankar's Knock Out, she's again attracted to the killer-hero, this time played by Sanjay Dutt. The two became professionally fond of one another while shooting for the comedy No Problem in Cape Town.

When Mani Shankar was looking for a bright intense young actress to play a television journalist it was Dutt who recommended Kangana to the director.