At age six, Loseth's family moved to Fort Nelson, British Columbia then in the year before he graduated high school they resettled in Grand Forks.
During his career, he was the Champion rider at Hastings Racecourse a record eight times and in 1984 earned another Sovereign Award as his country's Outstanding Jockey.
In 2001, he was voted the Avelino Gomez Memorial Award, an honour given to a jockey who has made significant contributions to the sport of Thoroughbred racing in Canada.
He had five wins in one day at California's Golden Gate Fields and won six races on three occasions (1974, 1976, 1994), doing it twice in Vancouver and once at Longacres Racetrack in Renton, Washington.
On April 9, 1984, Loseth equaled the North American record for most wins in one day when he won eight races on a single racecard at Hastings Racecourse.