Amir Khan may be one of the greatest boxers to ever grace UK boxing and has proven this by fighting in multiple weight divisions.

Even though he may not have had the desired success in each of the weight classes he's competed in, you can't say he didn't give it a go.

Here, we're going to take a look back at Khan's boxing journey, and just how his body and physique has changed in his 20-year career.

Khan bust onto the UK boxing scenes when the then 17-year-old brought back a silver medal from the 2004 Athens Olympics.

Back then, he was a baby-faced youngster, with a small physique to boot, but that was all about to change as he stepped into the professional world.

Read more: Amir Khan vs Kell Brook: Date, UK Start Time, Ring Walks, Card, Live Stream, Odds, Tickets, Stats And Everything You Need To Know

LONDON - JULY 9: Amir Khan of Great Britain poses for photographs during a press briefing as Britain's only Olympic boxing representative, at The Fitzroy Lodge on July 9, 2004 in London. The 17yr old Khan will be the youngest boxer at the Athens Olympics. (Photo by Ian Walton/Getty Images)

After bringing back the silver, Khan turned professional and started fighting in the lightweight division.

However, he suffered a shock loss to unknown Colombian boxer Breidis Prescott, which was when questions started to arise about his chin, and whether he would be able to hold his own in the big leagues.

LONDON - JULY 13: Amir Khan stands on the scales during his weigh in at the The O2 Arena on July 13, 2007 in London, England. Willie Limond v Amir Khan and Matt Skelton v Michael Sprott amongst others will fight in the O2 Arena on the 14th of July. (Photo by Dean Mouhtaropoulos/Getty Images)

Ultimately, however, he had nine fights at lightweight and won eight of them. Not bad. Not bad at all.

The lad from Bolton then moved up to light welterweight, where straight away he had a chance to win the WBA title against Ukrainian Andreas Kotelnik.

Khan put on one of his best performances ever and clinched the belt and went on to dominate the light welterweight division.

He did, however, lose to Lamont Peterson and Danny Garcia, but the former later failed a drug test.

MANCHESTER, ENGLAND - JULY 18: Amir Khan celebrates after defeating Andreas Kotelnik to become the WBA Light Welterweight Champion on July 18, 2009 at the MEN Arena in Manchester, England. (Photo by John Gichigi/Getty Images)

Khan did not want to stop there, however, and wanted to fight the big dogs in Floyd Mayweather and Manny Pacquiao. Chasing those big-name fights, the Brit decided to move up a weight class once more, this time entering the welterweight division.

However, Khan failed to land those fights and had a rather forgettable time in the weight class.

LAS VEGAS, NV - MAY 02: Boxer Amir Khan poses on the scale during his official weigh-in at the MGM Grand Garden Arena on May 2, 2014 in Las Vegas, Nevada. Khan will meet Luis Collazo in a welterweight bout on May 3. (Photo by Ethan Miller/Getty Images)

Finally, Khan moved up to the middleweight division, and back in 2016, fought Mexican boxer Saul 'Canelo' Alvarez for the WBC middleweight title.

Khan was brutally knocked out by Canelo with a big right hand as he struggled to prove himself in the division.

LAS VEGAS, NEVADA - MAY 06: Amir Khan poses during his official weigh-in at T-Mobile Arena - Toshiba Plaza on May 6, 2016 in Las Vegas, Nevada. Khan will meet Canelo Alvarez in a WBC middleweight title fight on May 7 in Las Vegas. (Photo by Christian Petersen/Getty Images)

It’s safe to say that Khan has put his body through a lot in his 20 years in boxing, and he is set to do it again as he finally lines up against Kell Brook this weekend.

The pair will meet on Saturday night at the AO Arena in Manchester and they will fight at catchweight.

Going by the above image, it's clear to see Khan is in great shape and ready for war this weekend.

You may not like or rate Amir Khan, but one thing is for sure, you have to respect the work he's put in over the years.