According to The Hollywood Reporter, the actor had to undertake such a step after a photo was leaked, thereby giving fans a sneak peek of the costume he will be wearing for the upcoming season of 'Flash'.
He is well known for playing the lead role in superhero TV series 'Flash'.
In his Instagram post, he wrote, "I've had 20+ years of kids and adults telling me or my parents I was too thin. I've had my own journey of accepting it. But there's a double standard where it's ok to talk s--- about a dudes (sic) body."
Grant in his post further mentioned that at every point of time he stays in the best shape possible. To all those calling him thin, he admitted on being naturally thin and it is evidently hard for him to become fatter.
"I'm happy with my body and who I am and other kids who are built like me and thinner than me should be able to feel the same way. Not only that, but they should be able to feel like THEY could be a superhero on TV or film or whatever it may be someday," Gustin further added.
The Season five of 'The Flash' is set to hit TV screens on October 9. (ANI)