The Aussie actor seemed several stone lighter while out and about in Sydney yesterday.
It came after the 47-year-old star embarked on a fat-fighting mission this summer in a bid to shift the pounds he piled on over the previous few years.
He revealed on Twitter: "Two separate work outs this morning, body movement for an hour +, then body movement with weighted objects hour."
In another post in June, he said: "Walked 8km today. Aim to be taking in roughly 2400 cal/ 2600 cal incl all beverages."
He even had some advice for porky followers looking to battle the bulge: "Join the Riley St gym, trainer there is Chris Feather, just start, that's the hardest bit, everything flows from that."
Since starting his workouts, Russell has rarely been seen in anything other than a tracksuit, and yesterday was no different.
The star, who famously played General Maximus Decimus Meridius in the 2000 film, tugged at his trousers, possibly chuffed to be grabbing a handful of excess material.
By contrast, the actor had no room to breathe in a sporty red top he wore at a charity cricket match in March.
Back then, his bloated stomach pushed his shirt to its limit as he watched the action pitch-side in Wellington, New Zealand.
Russell has intentionally gained weight for movie roles in the past, including 2008 thriller Body Of Lies.
At the time he revealed that he gorged on burgers at breakfast and cupcakes to plump up.