The Energy Clock: Energy Levels & Time of Day

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Our body’s circadian rhythm regulates our body functions. Therefore, our energy levels vary with the time of the day. Learn more about your body’s energy clock.

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Have you ever woken up earlier than you expected, as your eyes open to the brightness of the daylight? This is one of the ways that our body’s circadian rhythm helps to regulate and synchronise our body functions with night and day. These functions include sleep, appetite, and alertness. The circadian rhythm is the natural process that the internal body clock goes through on a 24-hour cycle, primarily responding to light and dark. For example, the sleep-wake cycle is one of the circadian rhythms. The circadian rhythms are connected to an internal clock, a group of nerves located in the hypothalamus in the brain. It’s highly sensitive to light and controls the production of the natural hormone melatonin. At night, when darkness falls, melatonin is released from the pineal gland in the brain into the bloodstream. Melatonin helps us feel drowsy, thereby helping to regulate the body’s circadian rhythm, synchronising sleep with night. When dawn breaks and light appears, this tells the body to stop producing melatonin. The brain then releases a series of hormones, including cortisol, which help to make sure you are alert and awake. Exercise, food intake, body temperature, and social interaction are other signals that can affect the internal clock, but light is the most important influence on circadian rhythms, according to The Sleep Foundation. In fact, light is such a powerful cue that some people can suffer from seasonal affective disorder during winter. The lack of sunlight during this season can hamper the circadian rhythm by releasing more melatonin, which can lead to people being more prone to low mood and sluggishness during this period. This is an example of when the body clocks can go off track. Other examples include jet lag and shift work when, for example, the external cues of light and dark fall out of sync. This can disrupt sleeping, eating patterns, mood and alertness. For most healthy adults, the circadian clock will reset every 24 hours. However, there are different chronotypes, which means that some people may feel more alert at night, commonly referred to as “night owls”, while others feel more alert in the morning, often called “early morning birds.” According to Harvard University, our circadian type is genetically determined and cannot be changed, although, over time, our circadian sleep phase moves towards the earlier stage of the evening. Knowing all this, we can take advantage of and schedule certain tasks to align with our circadian rhythm. Here are some lifestyle strategies we can implement at each stage of the body’s circadian rhythm to maximise our body’s energy potential.

Why should you be waking up early?

Exposure to light in the morning helps synchronise the clock, so you may benefit from keeping the curtains slightly open overnight for some light to pour into your bedroom when you wake up. If you are the type to wake up ready to take on the day, then you may want to schedule your work tasks for earlier in the day, and the same goes for exercise. On the other hand, if you can hardly open your eyes when the alarm goes off, you may benefit from starting with some relatively easy, monotonous tasks before progressing to the harder tasks. For exercise, it might be better for night owls to start with some gentle stretching or meditation to physically ease into the day.

Navigating the afternoon dip

According to Northwestern Medicine, the normal circadian cycle includes a period of sleepiness or decreased alertness in the afternoon. That late afternoon lull could do with some help from an exercise session to help move more oxygen-rich blood around the body and provide an energy boost. And if the sun is shining outside, this exposure to light, according to The Sleep Foundation, can help to stabilise circadian rhythms and make it easier to fall asleep early. It also reports that studies have found exercise can help increase the amount of slow wave deep sleep. Northwestern Medicine recommends reaching for healthy foods with protein, fibre, complex carbohydrates and magnesium that will take longer to digest and, therefore, extend your energy.

The evening wind down

Try to keep your bedroom at a cool temperature and dimmed, as darkness and lower body temperature promote deeper sleep. Exposure to bright light, such as from computer and phone screens, can cause disruption in the circadian rhythm, preventing sleep.

Tips for optimising our energy levels to our internal body clock

Consistent sleep routine

The Sleep Charity advises that it is important that we strengthen our body clocks to develop regular sleep and wake up time. Ensuring a consistent sleep schedule by getting up and sleeping at the same time each day as much as possible may help with this.

Eating according to the circadian clock

John Hopkins Medicine describes chrononutrition as the timing of your food intake in relation to your circadian clock. It discusses that research tells us that irregularity in meals, such as eating at inconsistent times or skipping meals, can all influence the circadian clock and metabolism. For example, although research on this is in the initial stages, according to The Sleep Foundation, experts currently think eating between 8 a.m. and 6 p.m. may be the ideal schedule for those wanting to align with their circadian rhythms.

Exercise

There is no evidence to suggest there is one perfect time of day to exercise for sleep, reports The Sleep Foundation. The right time to exercise will depend on one’s chronotype as well as age and any health conditions. For example, for an early morning person, it would be ideal to exercise in the morning, whereas a night owl may exercise at night and still be able to get to sleep afterwards. According to the Sleep Foundation, aerobic exercise in the morning or afternoon stimulates earlier melatonin release and shifts the circadian rhythm forward. It also reports that for most people, if the exercise is moderate-intensity exercise and concludes at least 90 minutes before bedtime, this should not have a detrimental effect on sleep. This allows time for endorphin levels and core body temperature to return to levels that are conducive to sleep.