Saeju Jeong was born in 1981 in South Korea into a family of doctors. His father was an obstetrician and gynecologist who died early of lung cancer. Jeong did not become a doctor.
At 20 he started BuyHard Productions, a heavy-metal label, and then served in the Korean army as an IT specialist. He enrolled at Hongik University and dropped out in 2005, moving to New York with about $3,000. He took sales jobs and delivered food.
In New York he met Artem Petakov, a former Google engineer. They formed WorkSmart Labs in 2007, renamed it Noom in 2011 and raised a $2.6 million seed round led by Kleiner Perkins.
The CDC recognized Noom's diabetes prevention program in 2017. Revenue reached $400 million in 2020, and a $540 million round in 2021 valued it at $3.7 billion. Jeong stepped down as CEO in 2023.