According to a new study frequent flyers jet lag can make obese and cause other metabolic problems by disrupting the daily rhythms of your gut microbes.
Organisms ranging from bacteria to humans have circadian clocks to help them synchronize their biological activities to the time of day. A new research has now shown that gut microbes in mice and humans have circadian rhythms that are controlled by the biological clock of the host in which they reside. Disruption of the circadian clock in the host alters the rhythms and composition of the microbial community, leading to obesity and metabolic problems. Source