Frequent travelers, particularly those who travel more often than they are home, are almost twice as likely to be obese as anyone else. This is the conclusion of the first rigorous scientific study of the question (summarized nicely at BBC News). It is easy to imagine possible mechanisms by which travel could lead to obesity: airline food, the hasty and irregular meals of travel, disrupted routines, limited availability of exercise, limited sleep, time zone changes that affect sleep, air travel radiation, airport security radiation, and a greater exposure to infectious agents. Some experts say the stress of a travel itinerary may be the main factor; others, though, believe it is the combined effect of many small stresses.
Whatever the cause, the magnitude of the effect is not small. You don’t worry about a disease being twice as likely if it is something rare, but obesity is one of the most common medical problems people face. To look at it another way, I have made a big deal year after year about the differences in obesity rates between U.S. states, but the difference in obesity rates between frequent travelers and infrequent travelers is larger than the difference between one state and another.
This suggests a need for some people to travel less, perhaps 10 days a month instead of 20, and for all of us to learn how to travel better. Not everyone who travels most of the time has trouble with it. If we can learn what practices create a successful traveling lifestyle, we will be able to travel more freely — and surely some of the lessons will also apply to those of us who stay at home.