Wait for about two hours after a meal before running.
"For most people, two hours is enough time for food to empty from the stomach, especially if it's high in carbohydrate," says Colorado sports dietitian and marathoner Cindy Dallow, Ph.D. "If you don't wait long enough, food will not be properly digested, raising the risk of abdominal cramps, bloating, and even vomiting."
The Exception: You can probably run 90 minutes after a light, high-carb meal, while you may need up to three hours after a heavy meal that's high in protein and fat.