“In the past, if I have ever done a photoshoot with so much as a t-shirt on, I have starved myself for weeks in advance and then picked and prodded at every picture and then normally taken the picture down,” the Stay With Me singer wrote.
“Yesterday I decided to fight the f*** back. Reclaim my body and stop trying to change this chest and these hips and these curves that my mum and dad made and love so unconditionally.
“Some may take this as narcissistic and showing off but if you knew how much courage it took to do this and the body trauma I have experienced as a kid you wouldn’t think those things.”
He thanked photographer Ryan Pfluger and added: “I’ll always be at war with this bloody mirror but this shoot and this day was a step in the right direction.”
Smith previously stunned fans when he shed weight, which he partly put down to “not eating like a pig any more”.