Jewish runners are concerned that the October 9 race date will conflict with Yom Kippur, which requires worshippers to fast for a 25-hour period.
About two-thirds of the 45,000 runners at the starting line for the Chicago Marathon every year travel from outside Chicago to run. The event brings in big money to the city usually over the three-day Columbus Day weekend.
Chuck Aron plans to run his seventh consecutive Chicago Marathon in October, even though he's Jewish and the race falls the day after Yom Kippur this year.
"I cannot speak for every Jew, but I know I will be running the marathon this year. I know that I will be doing a form of fasting," Aron said.
Marathon runners usually drink lots of fluid and eat lots of carbohydrates in the days leading up to the race. The Chicago Marathon hosts a spaghetti dinner the night before.
Most runners spent months training for the race, and it leaves some Jewish runners this year with a difficult decision.
"It is referred to as the holiest day of the year. It is a sound day. It has spiritual impact. People take it seriously," said the Jewish Federation's Michael Kotzin about Yom Kippur.
Marathon officials say they plan the date years in advance and have to work with lots of partners including the city, the NFL schedulers and hotels. But they say they are sensitive to the issue for Jewish runners.
"It's a personal choice, obviously. We are sensitive to that, and we're looking at ways that as we move to the planning phase through the spring and fall of adjusting some things that can accommodate those that decide to participate," said Marathon Director Carey Pinkowski.
Chuck Aron says his faith includes a tenant to help make the world a better place, which he says he'll accomplish by running.
"In my opinion, the fact that I'm raising money for these three worthy charities, for me not to run would not make the world a better place," Aron said.
Aron has raised about $80,000 the last few years for various charities.
Marathon organizers are planning on extending the hours of the pasta dinner to accommodate Jewish runners, and working with the synagogues to pick up the packets before the race because they will be at synagogue.