“Any time you leave your general habitat, it’s throwing your gut microflora off balance,” says Brooke Alpert, a New York-based registered dietician. Sometimes, that begins before you reach your new destination: In some people, the very act of traveling from point A to point B can cause constipation. Movement stimulates the gut, so sitting on a plane or in a car for long periods of time can cause the intestines to clog; ignoring the urge to go while in the air or on the road can also make it more difficult once you finally sit down on the toilet.
Time differences can also pose a problem. Many people have a normal bowel-movement routine, pooping at regular intervals throughout the day. But when jetlag or a new time zone shifts that schedule ahead or backwards by a few hours, it can mess up that routine, causing constipation.
Even the stress of traveling can make it difficult for people to poop while they’re away. Researchers have nicknamed the gut “the second brain” for the millions of neurons that line the intestines.