Darshan had to go on a strict grilled chicken and oil-free fish protein diet for three months and he was made to have seven small meals every day for "Mary Kom".
"I ended up looking so gaunt that I couldn't recognise myself in the mirror. But the effort seems worth it when women come up to me to say they want a husband like me. That feels good.
"It means my character works within the film's context. Now I need to regain some weight as I've become too gaunt. But I want to keep my six-pack," Darshan said.
He made a valiant effort to look convincing as Onler in the film opposite the National Award winning actress Priyanka Chopra.
"It was a challenge. But I was ready for it. I've been doing theatre for ten years. My acting guru is Naseeruddin Shah. Everything I know about acting is what I've learnt by watching him. At his age, he is so energetic and passionate about his work. He was my inspiration for all the hard work I put in to play Onler in 'Mary Kom'."
On Teacher's Day Sep 5, when the film hit the screens, Darshan showed "Mary Kom" to his guru. His words of praise meant the world to Darshan.
"I waited for Naseer saab to see my film. I've trained under him for ten years. What better Teacher's Day gift for me than to show my labour of love to my guru?"
Darshan says he likes to spend time with creative people.
"Whether it is Naseer sir or Sanjay Bhansali sir, just being with them is such a learning experience. I feel like a student whenever I'm with them."
Meanwhile, the gifted young actor has also completed work on Navdeep Singh's "NH10", where he is cast opposite Anushka Sharma.
Not willing to divulge much about his role in "NH10", Darshan said: "All I can tell you is that I play a character very different from the one in 'Mary Kom'. In fact, it's quite the opposite.
"In 'NH10', I am aggressive, insensitive and insufferable. Not the kind of guy any girl would want to marry."
So who's Darshan marrying in real life?
"At the moment, there is no one in my life. I'm married only to my work," he said.