Fat Ass events are an ultrarunning tradition. The tradition dates back to 1978 in California when Joe Oakes needed to come up with a 50-mile qualifying time for the Western States 100-mile Endurance Run.

The only local distance event he could find was the 50 mile Christmas Relays which required a team of 7, so he entered himself for each of the 7 legs and attracted 10 teams to accompany his solo attempt. Organizing the relay was a chore, so the next year (1979) Joe just invited anyone who wanted to run an informal 50-miler to join him. He called it the Fat Ass 50.

The concept of low-key, no frills, low or no cost events has struck a chord with experienced, self-sufficient runners. The name Fat Ass has stuck for this type of event and numerous Fat Ass events have sprung up around the world.

Another Western States 100-mile participant, Ean Jackson, hosted the first Fat Ass 50 kilometer run in Canada on New Years day in 1993. Inspired by Joe Oakes, his objective was to create an annual hangover cure for himself and a few ultrarunning friends that could be totally managed over the Internet, leaving him free to run with his friends rather than fret about the details of event management.

Since 1993, the Vancouver Fat Ass 50 has grown steadily in popularity and notoriety. The concept of providing detailed course directions to each participant and minimizing course markings was an early innovation. Along the way fellow ultrarunner, Sibylle Tinsel, organized a night run and other free oddball running events in Vancouver. The concept has grown to include other endurance sports such as triathlon and adventure racing.

The challenge of linking athletes with enthusiastic hosts of fun, low-key, free events became the genesis for Club Fat Ass. Club Fat Ass was founded in 2003.