Participating in the health improvement plan, which involves annual screenings and follow-up phone calls addressing concerns that turn up, won't cost the city workers and their spouses anything, Rahm said at a Friday news conference.
"The only thing that won't be free is not trying," the mayor said.
The program is projected to save the city $20 million the first year, a significant chunk when city officials are trying to plug a $636 million budget hole, the Chicago Tribune reported.
The program has the backing of Chicago Federation of Labor President Jorge Ramirez, who noted the city's union workers won't be required to meet any health standards.
"It doesn't mean you absolutely, positively have to succeed," Ramirez said. "It means you need to try."
City police union leaders aren't on board, though.
"Employees shouldn't be penalized $50 [per month] for them and $50 for their spouse, just because they don't want to participate in this program," Bill Dougherty, first vice president for the Fraternal Order of Police, said.
Emanuel explained the intent is for the municipal effort to mirror success the private sector has experienced implementing preventative programs to hold down healthcare costs, the newspaper said.
"You can't ask the public to pay for something that you need to take responsibility [for]," he said. "We will help you be a good steward of your health, but if you choose not to, you'll pay that price, and that's the price you'll pay."