Our internal circadian rhythms, or our body clock, when working correctly, is responsible for waking our bodies up in the morning and ensuring they get a good night’s rest.

In a healthy person, cortisol levels peak at around 8am, which wakes us up (in theory), and drop to their lowest at 3am the next day, before rising back to its peak five hours later.

Ideally, this 8am peak will be triggered by exposure to sunlight, if not an alarm. When it does, the adrenal glands and brain will start pumping adrenaline. 

By mid-morning, the cortisol levels start dropping, while the adrenaline (for energy) and serotonin (a mood stabiliser) keep pumping. 

At midday, metabolism and core body temperature ramp up, getting us hungry and ready to eat.

After noon, cortisol levels start their steady decline. Metabolism slows down and tiredness sets in. 

Gradually the serotonin turns into melatonin, which induces sleepiness. 

Our blood sugar levels decrease, and at 3am, when we are in the middle of our sleep, cortisol levels hit a 24-hour low.

Read more at DailyMail.co.uk