डॉ. पी.डी. गुप्ता बता रहे हैं सेहतमंद रहने के लिए हम कब क्या करें?

When to do what : Body’s Best Time for Everything

Author : Dr. P. D.GUPTA

(Former Director Grade Scientist, Centre for Cellular and Molecular Biology, Hyderabad, India)


If you want success in life, learn “When to do what” is the best formula to follow.  That being said on the basis of the earth goes around the Sun in a single day (24hrs) which results in the formation of Day (12hrs light) and Night(12hrs dark. It takes about a month for the Moon to orbit Earth (27.3 days to complete a revolution, but 29.5 days to change from New Moon to New Moon). The Moon makes its own light (the same way the Sun does). The Moon reflects the light of the Sun, just as the planets do. The moon moves around the Sun at the same time it moves around the Earth. Perhaps the best answer is to say the the moon interacts with both the Earth and the Sun at the same time. This is what we call "physics" of time and this we described in our books “Clock within us” and the other book is with the title “Dark side of The Night Light”.  

Above mentioned events are going on for millions of years for setting time for us. During these mega events, evolutionary process, a tiny biological clock was also established which regulates human activity. Every human being carries it from birth to death. Of course, age has own influence on it. There’s an ample amount of research that supports the notion that the human body has a biological clock, which affects everything from sleep to athletic performance. Human body also has circadian rhythms, which help with body temperature regulation, eating habits and digestion, and other bodily functions. Timing plays a big role among other things we do every day. So   looked into how our body responds to timing and how we can utilize that knowledge. It turns out that we actually have a very sophisticated internal body clock that governs almost everything we do, without us even realizing it. 

Working of the body  

Our body clock is a small group of cells made up of unique ‘body clock’ genes. These cells turn on and off and tell other parts of the body what time it is and what to do. In fact, most of our individual organs have their own internal body clock cells as well. So let’s take a look at how the internal body clock affects everything we do, and what the best time is for our body to engage in different daily activities.

Eating – Which meal at what time?

By far one of the trickiest topics to tackle is the optimal timing for eating. A quick search on Google reveals that there are as many viable diets as there are people. And yet, there are some great, general guidelines that we can follow. A recent study in Cell Metabolism tried to find out, given all things equal, if timing actually makes a difference. 2 groups of mice were put onto the exact same diet in terms of caloric intake. The only difference was that the first group had access to the food all day round, whilst the second group only for 8 hours during peak activity.The result according to the researchers was stunning:

The mice that ate only while active were 40% leaner and had lower cholesterol and blood sugar.

So, limiting your food intake to your 8 most active hours during the day could be a good idea. We can also dig a bit deeper into the optimal time for eating dinner in particular: When we should eat dinner?

When it comes to dinner, eating late generally conflicts with our internal body clock because it’s starting to wind down and get ready for sleep. If we’re simply not set up to process the food we’re taking in, it’s probably not the best time for a big meal.

Nutritionist Linda Morgan from the University of Surrey wanted to see how efficient we are at processing food at night compared to in the morning. She conducted an experiment where participants were given the exact same foods at night and in the morning. Then she tested their blood glucose levels to see how much glucose their bodies were hanging onto. Morgan says blood glucose levels indicate how efficiently our body is processing and storing glucose, and high levels of glucose in the blood after a meal can point out future risks like diabetes. Her experiment found that blood glucose levels after an evening meal were much higher than when the exact same meal was eaten earlier in the day.

Morgan says, we should try to get most of our calories earlier in the day and have lighter earlier evening meals when possible.

Sleeping – How long and at what time?

While some of us identify as night owls or morning larks, most of us actually have a fairly regular time when sleep benefits us most. Professor Jim Horne from Loughborough University says that we’re naturally designed to have two sleeps a day: a long one at night and another one in the early afternoon. Early afternoon is when our energy naturally dips lower than usual and we have a harder time focusing. The idea that we should sleep in eight-hour chunks is relatively recent. The world’s population sleeps in various and surprising ways. Millions of Chinese workers continue to put their heads on their desks for a nap of an hour or so after lunch, for example, and daytime napping is common from India to Spain. This is our internal body clock saying it’s a good time to go to sleep, so if you’re planning a nap—slot it into this part of your day!

Although everyone is different to some degree, we actually all start out as morning people, and continue this way until around age 10. From ages 10–20 we start to sleep and wake up later and later until around 20 years old, when the pattern starts to reverse again and we start waking up earlier. Eventually, around age 55, we are going to sleep and waking up at roughly the same times we did when we were 10 years old. So, age has a huge bearing on how our body clocks operate and what our optimal sleep times are. You’re probably familiar with how teenagers prefer to sleep in late and go to bed late, but it turns out it’s not just teenage laziness (although it is “just a phase,” since these tendencies lessen as we get older).

Teenagers are biologically predisposed to sleep and wake later than anyone else. This means they’re often struggling with important cognitive work at school during their least optimal times. A study of school students’ memory function in the UK actually showed that students performed 9% better on the same type of memory tests in the afternoon as they did in the morning. Another myth, similar to teenagers’ laziness when going to sleep is the fact that we need 8 hours of sleep each night.  


When choosing a time of day to exercise, paying attention to your body clock can improve results, as well as overall happiness through exercising. A general rule: later is better. For runners, cyclists and other endurance athletes, the morning is the worst performance time. Professor Greg Atkinson from Liverpool John Moores University says, “Almost every world record in track-and-field athletics and cycling events has been broken in the afternoon or evening.”

This could be a result of our body temperature being at its peak later in the day, giving us a natural ‘pre-game warmup’ in a sense. Our receptiveness to pain is also lower in the afternoon, meaning we can push further in endurance sports. Blood pressure is also a factor in our exercise routines. In the first three hours after we wake up, our blood pressure raises the most out of any point in the day. Our blood vessels open up more to allow for blood flow later in the day, our blood is not as sticky then and we have a natural drop in blood pressure in the afternoon. All these described in the book ‘Exercise for health and Beauty” written by me.

Exercising in the morning was found in an experiment to either increase blood pressure or not make a difference at all. In the evening, however, exercise was found to reduce blood pressure by 10–11%. Physical performance is higher, and risk of injury is lower, between 3 p.m. and 6 p.m. The National Sleep Foundation reports that exercise in the afternoon can help deepen shut-eye and cut the time it takes for you to fall into dreamland. But, they caution, vigorous exercise leading up to bedtime can actually have the reverse effects. Afternoon exercise can even help us sleep better  For other athletes, however, the morning could be the optimal performance time. Balance, for instance, is higher in the morning, so gymnasts might perform better then.


It turns out that circadian rhythms really affect how we work as well, so we all have peaks and troughs in our physical and mental capacity daily to get work done. The interesting part of this is that the type of work we’re doing makes a difference to which time of the day we should choose to do it in. Here’s how it breaks down: If you’re a morning lark, say, you’ll want to favour those morning hours when you’re feeling more fresh to get your most demanding, analytic work done. Using your brain to solve problems, answer questions and make decisions is best done when you’re at your peak, according to Scientific American: Numerous studies have demonstrated that our best performance on challenging, attention-demanding tasks—like studying in the midst of distraction—occurs at our peak time of day. When we operate at our optimal time of day, we filter out the distractions in our world and get down to business.

For night owls, this is obviously a much later period in the day.

On the other hand, if you’re trying to do creative work, you’ll actually have more luck when you’re more tired and your brain isn’t functioning as efficiently. This sounds crazy, but it actually makes sense when you look at the reasoning behind it. It’s one of the reasons why great ideas often happen in the shower after a long day of work. If you’re tired, your brain is not as good at filtering out distractions and focusing on a particular task. It’s also a lot less efficient at remembering connections between ideas or concepts. These are both good things when it comes to creative work, since this kind of work requires us to make new connections, be open to new ideas and think in new ways. So a tired, fuzzy brain is much more use to us when working on creative projects.

This Scientific American article explains how distractions can actually be a good thing for creative thinking:

Insight problems involve thinking outside the box. This is where susceptibility to “distraction” can be of benefit. At off-peak times we are less focused, and may consider a broader range of information. This wider scope gives us access to more alternatives and diverse interpretations, thus fostering innovation and insight.

How light affects our body clocks

Light is the single biggest external factor that affects our internal body clocks.

Each of us has a slightly different internal time, which can range from a 22 hour cycle (a fast body clock, associated with morning larks) to a 25 hour cycle (a slow body clock, which night owls would have). The average is around 24.5 hours. Sunlight helps us to adjust this internal time cycle each day to synchronize it with the world’s 24-hour cycle. It works like this: light hits the back of our eyes and travels into our brains, triggering the release of chemicals onto our body clock cells. This tweaks our internal time to be either slower or faster, making it exactly 24 hours. This also means that the more sunlight your eyes receive during the day can affect your clock by slowing it down or speeding it up when you don’t want it to. If you get lots of light in the morning, this will speed up your body clock and help you wake up earlier. Getting lots of light in the afternoon and around sunset will do the opposite—slow down your body clock and help you stay up later into the night.

This is probably the best trick I know for helping your body to adjust to a new time zone after flying halfway around the world, so it’s great to understand how it really affects our bodies! Our dependence on light to keep our body clocks synchronized with the day’s 24 hour period is affected by our age, just like our sleep patterns are. As we get older, two main things happen that relate to this:

Our eyesight worsens, and we receive less light into our eyes

Our body clock becomes less active

Both of these things make our body clocks run slightly out of sync with the world. We start waking up a lot during the night, and often waking up far earlier than we’d like to. This is because the lack of light coming into our brains through our eyes gives a much weaker signal to our body clock cells to adjust them to a 24-hour period.

And although we don’t lose any of our body clock cells, much fewer of them are actually active as we get older.

What’s also important to consider here is that the importance of lighting in your office or at home is tightly connected to the temperature in your workplace too. Make sure that both are aligned to get an even better focus on your activities. There’s still hope, though. An experiment that tripled the amount of light dementia and Alzheimer’s patients received during the day saw improvements in mood, better sleeping patterns and improved cognitive functions like memory and slower deteriorate of physical functions.

Some other cool facts

There are some other areas that are affected by our body clocks that I found interesting. Here are some of my favorite facts that I found out, mostly from the BBC video mentioned at the top of this post (it’s pretty amazing—I’d recommend watching the whole thing if you have time).

The best time to drink In the late afternoon/early evening our body clock is at its peak, so alcohol will have a lower effect on our cognitive ability. Lucky for us, this is right about the time for post-work drinks, so we can enjoy alcohol without it knocking us about like it would in the morning, or making us sleepy like it would at lunch.

The best time for medication Administering medications like chemotherapy which can kill healthy as well as diseased cells can be hugely affected by our body clocks. This recent study showed that if fewer of our healthy cells are active when the medication is administered, it will hurt less of them and be able to target the diseased cells better.

The best time to have a baby Actually, this distinction is becoming less obvious as more and more births are affected by medical intervention, but the extremely relaxed state of our brains and muscles at this time and our lowered pain sensations mean not only is this a popular time for natural births to occur, but probably the best time you could choose as well. (The author has his own study and views)