Director Puri Jagannadh has released a special video featuring Nandamuri Kalyan Ram undergoing physical transformation for his next venture ISM, which is set to be released in theatres on 21 October.

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Actor-cum-producer Kalyan Ram took to the official Twitter account of NTR Arts on Monday morning and announced that he has a surprise for Nandamuri fans. Besides sharing a poster, the actor wrote: "A special surprise for you all from our dashing director Puri Jagannath at 6pm today #ISMOnOct21."

Puri Jagannadh, who has written the script and directed ISM, had also promised another surprise. The director tweeted: "A special #ISM surprise for fans, today at 6pm."

The producer of ISM unleashed the special video featuring Kalyan Ram's physical transformation on the official YouTube channel of NTR Arts at 6 pm. Later, Kalyan Ram shared the link of the video on its Twitter handle. He also wrote: "Check out the amazing transformation video of @NANDAMURIKALYAN.."

Kalyan Ram is playing an investigative journalist in the action entertainer ISM. He has done lot of hard work to flaunt a brand new avatar in the movie. The Pataas star has shed 12 kgs to sport a ripped six-pack abs in the film. He does not like fish, but he had to eat it to get the much-needed physical transformation.

Puri Jagannadh releases video of Kalyan Ram's physical transformation for ISM. Pictured: ISM posterTwitter/NTRArtsOfficial

The 1 minute 28 seconds-long special video shows Kalyan Ram doing workouts under the guidance of a fitness trailer. The video has come as a real surprise for Nandamuri family's fans, who are busy sharing the video on their Twitter and Facebook accounts. The clip is now going viral on the internet.

Aditi Arya is playing the female lead opposite Kalyan Ram in Ism, which features Jagapati Babu, Posani Krishna Murali, Jaya Prakash Reddy, Tanikella Bharani, Easwari Rao, Ajay Ghosh and Vennela Kishore in the supporting cast.

Anup Rubens has composed music for songs and background score, while Junaid Siddiqui and Mukesh G handled the editing and cinematography, respectively.