In 1994 Joe Takahashi and his team were responsible for finding the CLOCK gene which, when altered, increases or decreases the length of an animal's internal circadian rhythm. The gene plays a major role in the body's ability to keep time. 24 years later he's still researching the impact of that gene. “The CLOCK gene just keeps on giving,” Joe says, “as technology improves we've been able to look at it more deeply, and identify the targets of the CLOCK gene.” The big surprise for Joe and his colleagues was that those targets are everywhere. When the gene was first discovered Joe and his team believed that they were looking at a brain-specific gene, something that would only be expressed in the hypothalamus and control your brain's circadian clock; but what they found was much more complex. “The genes are actually expressed all throughout your body,” Joe says, “every cell in your body can have a circadian clock!” This realisation caused a massive shift in how we view issues like jetlag or sleep disorders, “they're not just brain disorders,” Joe says, “your whole body has to shift over.”
“Different tissues are sensitive to different signals, so that makes the system more complicated,” Joe says “For instance, your liver will pay more attention to when you eat than it will to [when you sleep].” It's in this way that getting out of sync, by changing time zone or your meal times, can impact your entire body. “If you shift a [rat's sleep cycle] 12 hours, some of the organs will go east to west, while the others go the other way around,” Joe says, “So, your body can be literally out of sync, with your organs working in different phases and times.” Until your body syncs up again this disarray can impact not just your sleep but your metabolism, immune system, sensitivity to UV, and a ton of other bodily systems.
Joe isn't opposed to people getting their bodies out of sync, after all he flew from Texas to Dunedin to give this talk, but in those first couple of days after landing somewhere new it makes sense to be a little more careful with our bodies as they adjust.