D'Amico, whose goal is to run a sub-2:36 marathon, a personal best with under 6-minute miles, is feeling good about his chances.
"I'm very confident going in," he said. "So far my body's reacting great. ... But it's a marathon. Anything can happen."
As his fan base is growing -- he has more than 2,400 "likes" on Facebook -- McRunner is using his challenge to give back to charity. Appropriately, D'Amico, who is not sponsored by or affiliated with McDonald's, is raising money for the Ronald McDonald House, contributing $1 for every fan, up to $2,500. His father is matching the gift, and others can contribute to the McRunner donation independently.
"I want to show this idea of life is about choices, and marathoning is no exception," he said. "It's just important that you approach everything in a balanced way. And if you make good choices, good things are going to happen. ... You put in the hard work and make good choices, you're going to get good results."