Of all the divisions in professional boxing, the heavyweight division is unique insofar that it imposes no upper limit on body weight. The heaviest, and tallest, world heavyweight champion in boxing history was Russian Nikolai Valuev, who held the World Boxing Association (WBA) for two spells, between 2005 and 2007 and 2008 and 2009. As the result of hormonal disorders known gigantism and acromegaly, both of which are characterised by excessive bone growth, Valuev stood 7′ 2″ tall and weighed in at a little over 348lb, at his heaviest, and weighed in at 328lb for his WBA heavyweight title defence against Monte Barrett at Allstate Arena in Rosemont, Illinois on October 7, 2006. ‘The Russian Giant’, as he was known, retired from boxing in November, 2009 with a 50-2-0 record.
In terms of size, Valuev may have been in a division of his own but, in recent years, one or two other gargantuan world heavyweight champions have graced the ‘squared circle’. Andy Ruiz Jr., for example, weighed in at a dainty 268lb when he caused one of the major upsets in boxing history by beating Anthony Joshua, by technical knockout in the seventh round, at Madison Square Garden, New York in June, 2019 to become unified world heavyweight champion. Ruiz Jr., a last-minute replacement for Jarrell Miller, had fought, and beaten, Alexander Dimitrenko less two months previously, so had only put on 6lb in the interim.
However, six months of inactivity before his rematch with Joshua, at the Diriyah Arena in Diriyah, Saudi Arabia, in December, 2019, clearly took its toll on Ruiz Jr.. His weight ballooned to just over 283lb at the weigh-in and his lack of fitness, coupled with more circumspect tactics by Joshua, led to defeat, not only by unanimous decision, but by a wide margin, too.