Om won the men's 56-kilogram class of weightlifting, turning in an Olympic record early in the day and then waiting around to see if his total stood up for a medal.
He competed in what is known as the B final, a gathering of contestants whose past record is not deemed good enough to be on the stage with the stars of the sport.
Instead of being an also ran, Om lifted a total of 293 kilograms, four more than that managed by China's Wu Jingbiao.
Wu has won the last two world championships in the weight class. Om became the fifth weightlifter in history to produce a winning total that is three times his body weight.
The bronze at 56 kilograms was won by Valentin Hristov of Azerbaijan, giving his country its first Olympic weightlifting medal.
Zulfiya Chinshanlo of Kazakhstan won the gold medal in the women's 53-kilogram class. She set an Olympic record of 226 kilograms while doing so and her clean and jerk lift was a world record 131 kilograms.
Shu-Ching Hsu of Taiwan won the silver and Cristina Iovu of Moldova took the bronze.
Om's gold medal for North Korea was its second of the Olympics. In two days of competition in London, North Korea has equaled its entire gold medal total from China in 2008.