Source: Choi Seunghyun (T.O.P)'s wikipedia page, with trusted references

Prior to his involvement with YG Entertainment, Seunghyun was an underground rapper under the name of Tempo, and a childhood friend of G-Dragon, another member and leader of Big Bang. G-Dragon stated that the two were "neighborhood friend[s] from middle school" and would often dance and rap together. Although G-Dragon later moved away and the two "became distant", he contacted Seunghyun again when YG Entertainment was scouting for candidates to create a boy band. The pair recorded several demos and sent them to Yang Hyun Suk, CEO of YG Entertainment, who later asked Seunghyun to audition. Seunghyun was initially rejected by the record label, which deemed him too "chubby" to fit the "idealistic version" of an idol. Seunghyun later stated that he "went home and exercised really hard because I wanted to join YG Entertainment." Six months later, he returned for another audition and was signed on. He reportedly lost 20 kg in 40 days.