Once you start run commuting you will quickly learn that lunches can be tricky. On my first run home I learned a valuable lesson, I need to eat an early lunch. I leave work around 4pm (I’m a morning person so I get into work early). That first day I ate lunch at 12:30pm. More than 3 hours should be enough time to digest before running. But it wasn’t, my 6 mile run home was plagued with worry about throwing up.
Overtime I’ve learned that if I eat at 11am or 11:30am my run home is much more comfortable. In addition to your lunch time you also need to be mindful about what and how much you’re eating for lunch. For me large fatty lunches (like pasta with cream sauce, stir fry with lots of oil, or even a hamburger and fries) sit in my stomach like a rock for hours making my run home much slower. I’ve found that foods like salad, Mexican, or chicken and rice work with my commute. The higher carb meals digest quicker and give the energy you need for your run home. In addition to lunch I also try to bring fruits and vegetables the day before a commute for snacks throughout the day if needed.
Keep in mind food digestion and running greatly depends on the person and the meal. My lunch issues might be exacerbated because I work in a valley and in the first half of my run I have 1.3 miles of uphill. If your commuting route is flat you might be able eat nearer to your return run.
As you start run commuting it will take some experimenting to find out your optimal lunch time and acceptable meals. Have fun with your commute and enjoy the experimenting.