Greg is currently preparing to take part in Channel 4′s Sink Or Swim, to raise money for Stand Up To Cancer, attempting to “erase the stigma” of being a non-swimmer.
However, when the former long jump athlete posted a picture of himself in training for the upcoming challenge, some of his Instagram followers were quick to pass comment on his body.
A day after sharing his training pic, Greg posted another picture of himself in the sea, explaining that he is not ashamed of how he looks.
“I was called out for having a dad bod yesterday as if that’s something to be ashamed of,” he wrote.
“I very much realise I’m not in the shape I was as a professional athlete. I’m fine with that, I love cake and beer…”
He also said: “Another dip in the great blue. I’m using the time I have to experience and develop skills in order to swim the Channel to the best of my ability.
“Four weeks ago I couldn’t swim at all. Now I’m prepping for one of the most epic challenges for Stand Up To Cancer UK.”
Sink Or Swim will follow the progress of celebrities “as they are pushed to their absolute limits” while learning to swim.
Olympic gold medallist Linford Christie, Blue singer Simon Webbe and ex-Love Island contestant Wes Nelson are among the other names taking part.