Photo: Rob Kardasian jokes about his weight gain...

The only biliogical male child of Kris Jenner, Rob Kardashian just revealed the guilty pleasure behind his weight gain when he took to instagram on thursday to share a flashback photo of himself from 2011, at sister's Khloe Kardashians birthday at Sugar Factory in Las Vegas and he wrote:

"Started right here with these milkshakes hahaha#throwbackthursday," he captioned the shot, which shows him sucking on a straw with three milkshake glasses in front of him.
The joke comes after he and his family have spoken out about his new fitness regimen.
The reality TV star has kept a very low profile since his dramatic weight gain in 2013, when he admitted to putting on over 40 pounds after his split from Rita Ora.