The 32-year-old WBC champ ballooned up to an astonishing 28st after his stunning upset against boxing legend Wladimir Klitschko in 2015.
Fury's battle with mental health issues outside of the squared circle has been well-documented, not to mention he dealt with drug abuse and alcohol-related issues as he suffered from depression.
The Brit superstar's Gypsy King Official Merch Instagram account recently uploaded a picture of Fury showing off his incredible physique amid ongoing talks over a unification clash with Anthony Joshua.
However, Fury's weight difference between 2017 to 2021 has been showcased in a side-by-side comparison on Twitter.
The heavyweight star's physique has left many fans stunned, especially after Fury recently claimed he was drinking "anything between eight, 10, 12 pints of lager a day."
The 'Gypsy King' told iFL TV last month: "I am not going to put all my eggs in one basket because I have been guilty of doing that before and, when the fight doesn't happen, that is when I end up in a massive depression and feel like killing myself.
"I am not going to say, 'It [the 'AJ' fight] is definitely happening in June or July.' I have stopped training at the moment, I am on holiday.
"I am drinking anything between eight, 10, 12 pints of lager a day, at the minute. But I am not eating so I am getting my calories through alcohol.
"I have trained and trained and trained with no progress so I am now a man of leisure."
Fury hasn't fought since his masterclass performance against fierce rival Deontay Wilder last February in Las Vegas.
The potential mega-unification clash between Fury and Joshua could take place in either June or July, though an official announcement for the bout hasn't been made.
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