Sanjay Dutt has been shooting with much younger Kangna Ranaut for Knock Out and if they look compatible in spite of the latter being half his age, it's all because of a special ketosis diet - a high-fat, low-carbohydrate food.

"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 having to give up his favourite food," a source close to Sanjay told IANS.

The 50-year-old, who is looking trimmer, plays an assassin out to get his victim with a sniper rifle in Mani Shankar's Knock Out.