Farstad won one Olympic gold medal and one European Championship in his three-year international career.

During the war, he trained weightlifting and gymnastics in Trondheim, and returned to international competition by winning bronze at the European Championship 1947, where he won the 1,500 metres, and silver at the World Championship, where he won both 500 and 1,500 m, and was 2.2 seconds from becoming world champion by virtue of winning three distances.

[1] Farstad was selected for the Norwegian team at the 1948 Winter Olympics at St. Moritz, and was a favourite on the 1,500 m. He won the race with a time of 2:17.6; though Swede Åke Seyffarth in a later pair was ahead on all three laps before the finish, but Farstad's final lap of 37.6 seconds was unbeatable, and Seyffarth finished 0.5 seconds behind.

[2] Two weeks after the Games, Farstad took part in the European Championships at Hamar, finishing fourth after placing 11th and 12th on the two longest distances, though he won the 1,500 m again.

At the World Championships in Helsinki two weeks later, however, Farstad fell down to seventh on the 1,500, two seconds behind winner John Werket, and finished eleventh in the allround standings.

He was beaten by Kornél Pajor on the 5,000 metres, who set a new world record, but still led by 2.2 points after the first day.