He's been served with a 30-day eviction notice and must be out by April 25.
"First of all we love Jim and second, we all love his protein shakes," said club member Marcia Saunders, of Newport Beach.
"No juice, no justice!" they chanted, with different members of the group taking turns leading the cheer. They paraded around the building, carrying signs and urging others to join them.
Some were wearing t-shirts emblazoned with a picture of Kim; many held signs, crafted with markers, cardboard and duct tape. Kim brought hand-made buttons, reading "Save the juice bar."
Every time someone walked in or out of the gym, the protesters would invite them to join the rally.
"Come on, join us over here! Let's save Jim's juice bar!" they shouted.
Newport Beach resident Brad Rodgers said he usually doesn't participate in protests, but he couldn't sit this one out.
"It's a good cause," Rodgers said. "This guy's got a lot on the line."
A manager at the Newport Center 24-Hour Fitness Saturday said he could not comment on the protest.
Known around the gym and nearby office buildings for his smile and healthy smoothies, Kim's built up a loyal cliental who said they'll do everything they can to convince management to reverse their decision.
Corona del Mar resident Victor Trujillo is one of many members who said they'll take their membership somewhere else unless Kim can stay.
"When he leaves, I leave, without question," Trujillo said.
Saunders is also looking for a new gym, one with better customer service, she said.
"You know what, they don't seem to care," Saunders said of the club management.
Kim, who's seemingly overwhelmed by the outpouring of support from his friends and customers, said he understands why he has to leave but doesn't know what his employment plans are for the future.