Wednesday 3 February 2016 15:35, UK
Amir Khan will be bulking up to take on Saul 'Canelo' Alvarez in May and he's not the first fighter to make an ambitious jump in weight...
The 29-year-old Bolton star will end almost a year of inactivity in Las Vegas against WBC middleweight champion Alvarez at a catchweight of 155lbs - more than half a stone more than he weighed for his win over Chris Algieri in May 2015.
Khan (31-3-KO19) operated at lightweight early on his career and won his first world title at super-lightweight when he outpointed Andriy Kotelnik in 2009. He went on to fight at welterweight for the first time in May 2014 but will step up once more to take on Mexico's 'Canelo' (46-1-1-KO32).
With the natural development of human bodies plus the lure of prestige, grudge matches and, of course, lorry-loads of money, stepping up weight classes is nothing new in boxing - so let's look back at four of the more eye-catching 'leaps of faith' made by fighters.
Leonard was an imperious boxer. A bona fide welterweight, ahead of this bout the American had been beaten just once in his professional career - a close points defeat to legendary Panamanian Roberto Duran he immediately avenged via eighth-round knockout.
In Hagler, Leonard was stepping up against a man who had just defended his WBC, WBA and IBF world middleweight titles with a typically-ruthless stoppage of No 1 contender John 'The Beast' Mugabi. Despite putting on nine pounds, few thought that Leonard would be able to deal with the sheer physicality and he heard the opening bell as a clear underdog.
A naturally-lighter, faster boxer against a heavy duty relentless puncher - ingredients for a classic. Certainly, the fight caused much controversy. Jose Guerra's scorecard of 118-110 in favour of Leonard stuck out a mile, but the underdog had his victory via split decision and Hagler would never been seen in a professional boxing ring again.
Roy Jones Jr's rise through the weight divisions saw him hailed by many as the best pound-for-pound boxer on the planet in the late 1990s, but eyebrows were raised when he bypassed the cruiserweight division to challenge Ruiz for the WBA world heavyweight title.
Jones Jr achieved world champion status in 1993 when he won a unanimous decision over Bernard Hopkins for the IBF middleweight crown and by 1999 he held three light-heavyweight world titles. Unable to agree terms to face Dariusz Michalczewski for a chance to unify the entire division, Jones Jr took a shot at the burly Ruiz.
The Floridian packed on around 18lbs for the contest but still gave away 33lbs on the scales to the champion in addition to three inches in height. Jones Jr's skills ultimately proved decisive though, as he boxed cleverly and used his superior movement to record a comfortable unanimous decision and emulate Michael Spinks by stepping up from light-heavy to win a world title in his first heavyweight bout.
Haye had fought at heavyweight before in his career - but has a fight ever looked like such a mismatch physically, before? The colossal Valuev was an intimidating presence at over 7ft tall and regularly weighing in at close to 23 stone. Haye was a cruiserweight world champion getting in with the heaviest of world heavyweight champions.
At 6ft 3in, Haye was dwarfed by his opponent but retained an air of confidence in the build-up and went into the fight as a favourite with the bookmakers. Billed as David v Goliath, the fight hinged on a meticulously-crafted game plan from Haye's trainer Adam Booth and the Londoner's impressively disciplined execution of it.
As Haye ducked and weaved his way to a majority decision, there was an extraordinary moment with a minute of the fight to go when the giant Russian was wobbled by a solid left hook to the jaw - dancing a dance towards the ropes as Haye leapt on to the offensive to cement victory.
In 1998, Pacquiao became a world champion for the first time - at flyweight (he weighed in at 112lbs). More than 12 years later, the Filipino legend took on the towering Margarito. Standing an inch shy of 6ft, the Mexican would enjoy a significant height advantage over the 5ft 5in Pacquiao.
In his previous bout; a successful WBO world welterweight title defence against Joshua Clottey, Pacquiao weighed in at 145¾lbs. Although he was stepping up to super-welterweight for the first and last time, a 31-year-old Pacquiao tipped the scales at 144½ ahead of taking on Margarito. That meant a five-and-a-half pound weight advantage for Margarito.
Despite the clear physical disparity between the pair, Pacquiao put on a master-class of boxing to become an eight-time division world champion. By the time the judges delivered a wide points verdict in his favour, Pacquiao had turned Margarito's face into a swollen mess.
