Inside every person's body is a master biological clock in the brain and many peripheral clocks. Living according to a schedule that does not suit your own clock seriously affects your health.
About 1/5 of the population in Western countries may put their health at risk simply by going to work. Working outside other people's usual hours is thought capable of contributing to obesity, diabetes, heart disease, cancer and even impaired brain function.
Scientists believe our bodies are programmed to operate in cycles known as circadian rhythms, and changes in routine caused by shift work or long-distance travel disrupt these rhythms.
According to studies, each person has not just one biological clock but a network of smaller clocks throughout the body. Humans and other mammals have a master clock in the brain called the suprachiasmatic nuclei (SCN), along with many peripheral clocks.
People taking long flights often try to minimize the time difference and post-flight fatigue by adjusting their routines to the new time zone. In a study on this issue, scientists wanted to see whether one factor—changing mealtimes—affected circadian rhythms.
They found that delaying a meal by a certain amount of time also produced a corresponding shift in some peripheral clocks, but did not affect the master clock. This is important because animal studies show that peripheral clocks take longer to adapt to a new rhythm.
The Rhythm of Eating
We know that eating at different times affects metabolism in different ways. The body has a natural circadian rhythm for blood sugar, meaning that if you regularly snack instead of eating main meals, your blood sugar will still vary with the time of day. Similarly, eating in the evening raises blood sugar and fat levels more than eating in the morning.
Some recent studies suggest that peripheral clocks outside the brain can synchronize with one another by restricting food intake to a few hours each day. But the complex nature of peripheral clocks makes them difficult to study, so scientists still do not fully understand how mealtimes help synchronize human circadian rhythms.
To overcome this obstacle, they examined how changing mealtimes affected the circadian rhythms of 10 healthy male volunteers. In the experiment, the volunteers ate 3 meals at fixed times for 5 days, then each meal was delayed by 5 hours for the following 6 days. Meals were designed to meet each volunteer’s metabolic needs, with the same calorie and nutrient content in every meal.
At the end of each stage, the scientists measured the volunteers' circadian rhythms under the stated conditions, allowing their biological clocks to run without being affected by external factors such as daylight and darkness.
Reset peripheral clocks
The study's most surprising result was that delaying meals by 5 hours also shifted blood sugar rhythms by nearly 5 hours. Markers of the master SCN clock remained unchanged; what changed was how a peripheral clock signaled instructions to the body in fat tissue, which was delayed after late meals. The researchers therefore suggested that changing meal times reset peripheral clocks without affecting the master clock.
The study also found that changing mealtimes and light exposure times can help the master and peripheral clocks shift at the same rate. This may reduce differences between the body's clocks and thereby minimize health problems.
Collected
