[1] He competed in the marathon event at the 2015 World Championships in Athletics in Beijing, China, placing 15th.

The prize winnings of US$200,000 represented a significant change of fortunes for the athlete and he remarked "I really don’t know what I will do with it".

[4][5] He made it three consecutive wins at the distance by topping the podium at the Orlen Warsaw Marathon in 2:07:57 hours later that season.

[6] After losing his winning streak on his international debut at the 2015 World Championships in Athletics, he returned to defend his Dubai title in 2016 and gave a strong effort with a personal best of 2:04:33 hours.

[7] Lemi won the 2016 Boston Marathon in a time of 2:12:45, confirming his place among the world's top distance runners.