The human body never stops, working around the clock as biological functions follow circadian rhythms, mental, physical and behavioral changes that follow an approximate 24-hour cycle. A new study demonstrates how humans reset their body clocks or “master clocks.”
Master clocks, a group of intercommunicating neurons or nerve cells in the suprachiasmatic nucleus (SCN), control circadian rhythms. The SCN, located in the hypothalamus, is a part of the brain that controls hunger, thirst and body temperature, is comprised of about 20,000 neurons.
A new study conducted by researchers at the University of Surrey in the United Kingdom examines how delayed meal times affect the master clock. The research team analyzed the effect of a 5-hour delay in mealtime on the master clock and its peripheral circadian rhythms.
The circadian rhythm, nutrition, eating patterns and human metabolism are all interconnected. However, the connection between circadian rhythm and meal times has not been adequately investigated.
The participants, 10 males, consumed three meals in 5-hour intervals each day over a 30-day period. Mealtime would either begin early, half an hour after waking or late, five and a half hours after waking.
All participants consumed meals early until their body acclimated and then switched to late meals for a total of six days.
All meals had similar calories and nutritional content.
The researchers measured the circadian rhythms of all participants in a 37-hour “constant routine,” a special protocol utilized in research that enables researchers to gauge circadian rhythm. Typically, the routine involves continual bed rest under constant illumination. However, in this study dim lighting was utilized, along with the consumption of snacks, consumed in spaced out on even intervals, no sleep and decreased physical activity.
The findings revealed that delayed mealtime did not effect sleep or appetite, nor was the master clock affected, as its biomarkers – for example, cortisol rhythms, melatonin and gene expression – remained unchanged.
However, blood glucose rhythms were delayed on average by 5 hours, when meal times were delayed.
“A 5-hour delay in meal times causes a 5-hour delay in our internal blood sugar rhythms. We think this is due to changes in clocks in our metabolic tissues, but not the ‘master’ clock in the brain.
We anticipated seeing some delays in rhythms after the late meals, but the size of the change in blood sugar rhythms was surprising. It was also surprising that other metabolic rhythms, including blood insulin and triglyceride, did not change,” the researchers wrote.
The research team also discovered that the rhythm of the expression of PER2 was delayed by 1 hour. PER2 encodes a very important clock component and its expression was delayed in adipose tissue. More specifically, the research team observed a fat tissue PER2 rhythm delay.
“Time meals therefore play a role in synchronizing peripheral circadian rhythms in humans and may have particular relevance for patients with circadian rhythm disorders, shift workers and transmeridian travelers,” the authors concluded.
The researchers noted that individuals who have circadian rhythm issues could attempt to consume meals at specific time intervals to reset their master clock.
The strategy could potentially help shift workers and those experience routine jet lag.
The study was published in the journal Current Biology on June 1, 2017.