The two-time Olympian ran his first long road race last September -- and won.
Danni Allen lost 121 pounds to win the show's $250,000 grand prize.
But he's not hanging up his racing shoes.
Approximately 15,000 slots are up for grabs.
Announcement comes on same day that three Kenyan marathoners get banned for doping.
The three-time Olympian will also run the Shamrock Shuffle in April.
The 26.2-mile race has become more competitive for both the men's and women's divisions.
We caught up with the newly-minted 2:07:47 marathoner.
The marathon rookie ran a 2:27:17 debut at Chicago this past weekend.
Over 1,300 runners came up empty handed at the end.