Our bodies have 2 systems that are closely related to circadian rhythm – what we call Central clock and Peripheral clock.
The central clock is said to regulate 10-15% of gene expression, and it is constantly updated based on (blue) light exposure, when light sensing molecules in our eyes* “charge” enough. Peripheral clock also governs many metabolic processes (3000-5000 genes in liver get turned on or
off based on time of the day), and it “starts ticking” based on the incoming nutrients.
If we don’t synchronize central and peripheral clock, processes in our bodies are also desynchronized. For example if we eat a meal in the evening, we “wake up” the peripheral clock making it think it’s still bright day, but at the same time central clock is already guiding us towards
sleep and changing our metabolic rate.
Many studies… confirm the importance of avoiding food intake prior to sleeping – with impact ranging from 70% lower body fat (…., study with mice) to significantly decreased recurrence of breast cancer (……, study with …. women).
Having consistent daily schedule of sleep and food intake makes the transition to new timezone easier – we can use meal and sleep timing to gently nudge body to adjust. On top of that we can use the peripheral clock “reset” in environment where we have little control over our light exposure (e.g.on a plane or at the airport).
*these light sensing molecules are not related to vision. Even people who were born blind will follow natural light/dark cycle as long as their melanopsin cells are intact.