Reports suggest that Karan, impressed by Ranbir Kapoor’s physical transformation for the Sanjay Dutt biopic, asked him about his trainer, and RK immediately put him onto his personal trainer Kunal Gir.

According to DNA India, Kunal says, “Ranbir told me Karan is interested in losing weight. After his children’s birth and his hectic lifestyle Karan felt he had put on weight and wanted to be fit again. Ranbir recommended me to him. Karan told me his immediate objective was to lose excess weight and get fit. Currently, he is following the ketogenic diet which includes no-sugar and no-carbs. He has to consume more fiber in his diet as his body type needs it. Hence Karan is eating more vegetables and meat now. While Ranbir had to bulk up and eat eight meals a day, Karan has lesser number of meals with less food as he has to burn fat.”

Recently, Karan Johar turned 45, and his birthday party was no less than a Bollywood fiesta with a guest list of 128 invitees comprising Shah Rukh Khan, Deepika Padukone, Aamir Khan, Akshay Kumar and his wife Twinkle Khanna (who is the filmmaker's best friend), Aishwarya Rai Bachchan and her husband Abhishek, Katrina Kaif and more.

Whereas, among youngsters were Shah Rukh's son Aryan, Saif Ali Khan's daughter Sara Ali Khan and Jhanvi Kapoor - Sridevi's daughter.