According to Official Guinness Records,
The heaviest person to complete a marathon weighs 193.96 kg (427 lb 9 oz) and was achieved by Charles Bungert (USA) while running the LA Marathon in Los Angeles, California, USA, on 17 March 2013.Bungert finished the race with a time of 8:23:40.
For a complete list of 2013 records, please visit 2013 Guinness Records in United States.