The actor revealed to Shortlist that it's nearly impossible for any actor to remain as toned in real life as they are on the big screen.
[Sylvester Stallone in 'Bullet to the Head]
"Looking as ripped as I do on the Bullet to the Head film poster is a temporary situation - you can't maintain it," he explained.
The star then quipped: "When I first saw myself [on the poster] I thought, 'F**k, I look sickly!' I'm actually very smooth in real life."
Stallone also acknowledged that he has been very self-conscious about his body at times, especially as he's grown older.
"I have all kinds of chest injuries; I tore my vein during Rocky II and had 60 stitches. If you've seen Rocky Balboa, you'll know how bad they look," he said.
"It got worse and worse, and people were saying, 'Urgh, has he got varicose veins?' So I thought, f**k it, and covered them with a tattoo of my wife. Then the tattoo started to grow and it went to a skull and before I knew it, I was a mural."
Stallone stars in his latest film Bullet to the Head as a hitman who teams with a Washington DC detective to solve two murders.
Bullet to the Head is now playing in the US and in the UK. Watch a trailer below: