Our obsession with digital screens is depriving us of sleep and hurting our health. Study after study shows that we are staying up till late, glued to our gadgets, which in turn leads to another unhealthy habit: night-time snacking. “Even healthy food eaten at this late hour is junk,” said circadian biologist Satchidananda Panda. “It is the timing of it.”
Panda, who grew up in Cuttack in Odisha, leads a research team at the prestigious Salk Institute of Biological Studies in San Diego in the United States. Broadly, he studies circadian rhythms, the innate timekeeping which tells living creatures, including humans, when to wake up, when to eat and finally when to sleep. Learning to take advantage of the body’s circadian rhythms could help in everything from losing weight to curing chronic ailments.
In June, Panda’s book The Circadian Code: Lose Weight, Supercharge Your Energy, and Transform Your Health from Morning to Midnight, which translates cutting-edge research in circadian biology into practical takeaways, was released. While it sounds like the title of a self-help book, there is plenty of science in it.
In a conversation with Scroll.in, Panda talks about the circadian clock, the link between the light-sensing protein and health and the importance of Time Restricted Eating. Edited excerpts:
What is the circadian clock? Why should we be in sync with it?
The circadian clock is an internal timepiece that regulates our daily patterns of behaviour and physiology. Initially, scientists thought that there was one master clock in the brain which controlled the entire body. In 1997, they discovered that almost every organ in the body has its own clock.
Almost every cell in the body contains one of these clocks. Each clock is programmed to turn on or off thousands of genes at different times of the day or night. All these clocks work in sync to keep us going. When our daily patterns of eating and sleeping are disturbed, our clocks cannot send out the right messages to these genes, and our body and mind will not function optimally.
If the disruptions continue for weeks at a time, there are big consequences. We may succumb to a variety of infections and diseases. Slowly, it is becoming clear that a disrupted clock is the mother of all maladies, and, in many chronic diseases, clock function is compromised.
You made a key discovery in circadian biology even as a postdoctoral associate...
For almost 100 years, scientists knew that there was a sensor that sends light signals to the master clock in the brain to tell it when it is morning and when it is night. Many individuals who are blind do know when it is day and when it is night without any external cues. So, sensing is different from seeing. How does this sensor work? Is it in the eye or elsewhere?
As it turns out, the light-sensing protein, melanopsin, is present in only a few thousand neurons in the eye, but they hook up directly to the brain area that houses the master clock. Sunlight is a rich source of blue light, which is what melanopsin senses. The prestigious magazine Science listed this discovery, made independently by five research teams, among the top ten breakthroughs of 2002. Since then, we have learned a great deal more about the link between melanopsin and health.
Light is not the only thing which affects the circadian clock in mammals, as you discovered...
We experimented on mice, which are typically nocturnal creatures. They eat at night. So, we fed them only during the day and to see what that does to their internal clocks. Surprisingly, we found that almost every liver gene that turns on and off within a 24-hour period ignored the light signal and synced to when the mice ate instead.
We learned that a daily eating-fasting cycle drives almost every rhythm in the liver. All the timing information doesn’t just come from the outside world through the eye’s blue light sensor. Just like the first light of the morning resets our brain clock, the first bite of the morning resets all other organ clocks.
So, you had a new handle to deal with the circadian clock in mammals?
Yes. We did experiments to test this theory. Research literature says that when mice are given free access to fatty and sugary foods, they become obese and diabetic within a few weeks. What we did was this: we gave one set of mice free access to the fatty diet for 24 hours [while] the second group had access to the same food for an eight to 12-hour period. What we found was startling: mice that eat the same number of calories from the same foods within 12 hours, or less, are completely protected from obesity, diabetes, liver and heart disease. When we put sick mice on scheduled feeding, we could reverse their disease without medication or change in diet.
Was that how you hit upon this concept of Time Restricted Eating?
Time Restricted Eating means taking in all your calories within a specific window of time, typically within eight to 11 hours. Sticking to such a schedule will help you lose weight, avoid chronic diseases and enhance your sleep quality.
Till we published these results, conventional wisdom said what we eat and how much we eat determines our health. But similar observations poured in from labs around the world, including studies on humans. Now we know that in addition to what, and how much we eat, when we eat matters. Time Restricted Eating helps you reduce weight, regulates blood sugar and keeps your heart healthy.
This research is ongoing. We have developed a free app called myCircadianClock that helps you keep track of daily behaviours such as eating, sleeping, exercising, and taking supplements and medications. Your data will help researchers understand how daily timing of behaviours influence health and well-being, while the app provides you personalised insights into your daily rhythms.
Can indoor lighting be made to sync with our circadian biology?
We now know a few things about how light affects our mental and physical well-being. By using a blue light sensor, our circadian clock recognises daylight, a rich source of blue light. Bright lights, exposure to blue light, inhibit the production of melatonin, a natural sleep aid.
So, newer smartphones and tablets are designed to change the background colour from bright white to a dimmer orange a few hours before bedtime. Using those settings is a start.
Meanwhile, researchers are figuring out how much light and what kind of light [meaning, which colour] we should experience, at what time, to promote health and mental well-being.
What are some lifestyle changes people in India might benefit from?
Even half a century ago, the common practice was to eat sparingly and finish eating the last meal around sunset or early evening. The Jains ate all their food before sunset.
Now, majority of Indians suffer from chronic circadian rhythm disruption because of their eating patterns. Some of this is shaped by culture and some by the new urban lifestyle. It is customary for people to wake up early and have a cup of tea or coffee and a snack. This breaks their overnight fast. The body can efficiently process food for the next twelve hours at best. But they eat dinner late, often after 9pm. More than a third of their food is consumed when the body cannot optimally process it. Consequently, the incidence of pre-diabetes, diabetes, hypertension, heart attacks and general inflammatory diseases are on the rise even in people in their 30s and 40s.
Those with long commutes may consider bringing breakfast with them and eating around 10am and to eat dinner with the family before 9pm. Such a simple lifestyle change can be the first step towards building other healthy habits of better food, little more physical activity and better quality of sleep. These will work together to prevent or reverse non-infectious chronic diseases that are afflicting millions in India.
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