When you eat is just as important as what you eat, according to a recent study published in Cell. Researchers from the Medical Research Council and the University of Manchester found that insulin plays a crucial role in communicating the timing of meals to cellular clocks found all over the body. In particular, eating at the “wrong” time can lead to spikes in a person’s insulin levels – which stimulates proteins that are not supposed to be active at that time.
In the study, the team looked at how the timing of insulin spikes affects the circadian rhythm, also known as the body clock, in a mice model. Their findings revealed that administering insulin at the “wrong” biological time – such as when they were supposed to be resting – caused a major disruption in the mice’s body clocks. The disruption, in particular, caused less distinction between day and night.
These findings could apply to humans as well. If a person eats at the wrong biological time, like late at night, it can adversely affect his or her body clock. This increases the risk of developing more serious conditions, like Type 2 diabetes and cardiovascular disease.
The study also highlighted how some normalized aspects of society, such as shift-work, sleep deprivation and jet lag, may negatively affect a person’s health in the long run.
The importance of the circadian rhythm
The circadian rhythm refers to the 24-hour biological cycle of each cell in the body. The inner processes of these cells affect the “rhythms” in a person’s physiology, like the rise and fall of cortisol levels.
It’s worth noting that a person’s body clock does not operate by itself. It is heavily influenced by the surrounding environment, primarily through exposure to sunlight and the timing of meals. For instance, lunchtime signals hunger and nighttime signals sleep.
The synchronization between the body clock, the interaction of cells and the surrounding environment is crucial to maintaining good health. Studies have shown that disrupting the body clock, such as in shift-work and sleeping late, has negative effects on the body.
Eating late at night is also a potential factor to consider when it comes to the body’s circadian rhythm. However, there was no clear understanding as to how the body clock reacts to meal timing, making it difficult to suggest solutions to the problem. In the study, the researchers were able to pinpoint the compound which connected the two – insulin.
What happens after eating late at night
Through experiments on cultured cells and mice, researchers found that insulin helps communicate meal timing to the cellular clocks across the body. When a person eats, the pancreas releases insulin. This acts as a timing signal for cells, and it stimulates the production of a protein called Period (Per).
The Per protein is essential to a cell’s circadian clock. Along with the Timeless (Tim) protein, their abundance and location affect the activity of various genes inside the cell and consequently, cellular timing.
“At the heart of these cellular clocks is a complex set of molecules [including Per and Tim] whose interaction provides precise 24-hour timing. What we have shown here is that the insulin, released when we eat, can act as a timing signal to cells throughout our body,” explained Dr. John O’Neill, the study’s corresponding author and a researcher at MRC.
Giving insulin to mice at a time they would be normally resting disrupted their normal circadian rhythms. This results in an imbalance in the Per and Tim protein levels inside the cell, disrupting the 24-hour cycle.
The disruption of circadian rhythms is known to have adverse effects. In an earlier study, researchers found that chronic disruption of the body clock in mice can lead to weight gain, impaired cognition and impulsiveness.
These studies have serious implications for human beings. Commonplace activities like shift-work, jet lag, and lack of sleep disrupt the body clock. According to the researchers, this disruption could potentially contribute to the increasing numbers and severity of diseases, including Type 2 diabetes and cardiovascular disease. (Related: Could chronic jet lag increase your risk of cancer? Study on circadian rhythm finds a link between body clock disruption and how tumors form.)
Finally, they suggest that proper meal timing, as well as exposure to daytime, may help maintain a healthy circadian rhythm.
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