Scientists have isolated the body-clock genes that control 24-hour light-dark circadian rhythm, and it’s now known that every cell in the body has a synchronized clock.
The 2017 Nobel Prize in Physiology and Medicine was awarded to three scientists who discovered the body clock gene and its critical role in metabolic function. In a world of 24/7 non-stop chaotic eating, relentless stress, continuous screen-gazing, sedentary lifestyle and sleep deprivation, time has become irrelevant. These constant 21st century disruptions of the powerful cellular body clock cycles (aka, circadian rhythm) are wreaking life-threatening havoc on mental and physical health, resulting in obesity, metabolic syndrome, cancer and diabetes.
“We didn’t realize at the time that this clock would be represented all over the body in many different tissues and control so many different biological processes that we go through every day,” says Michael Young MD, 2017 Nobel Laureate in Medicine and Physiology. “It left us with the understanding that our whole bodies are rhythmically active.”
Circadian Alignment is when the central and peripheral clocks are aligned: bright light during daytime, sleep at night, and food intake during daytime. Circadian Misalignment is when the central and peripheral clocks are misaligned: light at night, sleep during daytime, and food intake at night.
This misalignment has become normalized. According to a recent study of the eating habits of more than 34,000 U.S. adults, nearly 60 percent said it was normal for them to eat after 9 p.m.
Yet, time-restricted eating (12-16 hours of non-eating) has proven to be the best match to our circadian clocks. This means we need to eliminate nocturnal eating. We should stop eating by 6-7pm and not eat again for at least 12 hours (14 hours is the sweet spot).
Our bodies have evolved to process nutrients during the day, and to conserve energy at night. The body uses energy to repair all of its systems at night, while we sleep. Disrupting that natural rhythm can cause problems.
Several studies have found, for instance, that eating dinner within three hours of bedtime may worsen heartburn or acid reflux symptoms. And limited research has suggested that eating one to three hours before bedtime is associated with more disrupted sleep.
The most intriguing research on late-night eating, however, has focused on its relationship with body weight and metabolic health.
In one 2019 study of nearly 900 middle-aged and older U.S. adults, researchers at Brigham and Women’s Hospital in Boston found that those who consumed roughly 100 calories or more within two hours of bedtime were about 80 percent more likely to be overweight or to have obesity than those who did not eat during that window. Researchers have found similar results in adults in Sweden and Japan.
And in a 2023 study of more than 850 adults in Britain, those who regularly snacked after 9 p.m. had higher levels of HbA1c, a marker for diabetes risk, and greater spikes in blood sugars and fats after daytime meals than those who did not typically consume late-night snacks.
Research has also found that carbohydrates consumed in the evening result in greater blood sugar spikes than those consumed earlier in the day. That is in part because melatonin, a sleep-promoting hormone that increases in the evening, dampens the secretion of insulin, which regulates blood sugar levels. Elevated blood sugars could eventually damage blood vessels and increase the risk of developing high blood pressure and Type 2 diabetes.
Research suggests that it’s best to avoid eating for three to four hours before your usual bedtime. We should be eating during an 8-12 hour window, allowing 12-16 hours for regeneration. We should also be sleeping for 7-8 hours each night.
A regular bed time is critical for your health and wellness, as is a regular waking time. Additionally, sleeping too long can affect your ability to fall asleep that night. After a good night’s sleep, most people need to be awake around 16 hours before they feel sleepy again.
Going to sleep between 10:00 pm and 11:00 pm is associated with a lower risk of developing heart disease compared to earlier or later bedtimes, according to a recent study by the European Society of Cardiology. Early or late bedtimes may be more likely to disrupt the body’s circadian clock, with adverse consequences for cardiovascular health, according to the study’s authors.
The incidence of cardiovascular disease was highest in those with sleep times at midnight or later (25% higher risk) and lowest in those with sleep onset from 10:00 to 10:59 pm. There was also a 24% higher risk for falling asleep before 10:00 pm. Yes, the body clock is that precise and sensitive.
Humans are not nocturnal animals; we are diurnal. We need to honor our innate body clock by eating and sleeping in a manner that naturally suits us and promotes health.