00:00-02:59
Body enters shutdown
Sleep hormone melatonin peaking
Minimum levels of attention and vigilance
Brain washes itself and consolidates memories
It is well and truly bedtime. Hormonal changes in the body say it is time to be asleep. The brain is washing away the waste toxins built up during a hard day's thinking and the bowels are shut down for the night. If you're still awake be careful, levels of attention are at their lowest, making industrial accidents a risk on night shifts.
03:00-05:59
Body fast asleep
Minimum core body temperature
Severe asthma attacks more common
Most natural births occur
It's the heart of the night and your body is still some way off waking up and getting you out of bed. Sleep hormone melatonin levels are still high, but glide down as dawn approaches. Your core body temperature is notably cooler than any other part of the day as energy is diverted elsewhere, such as skin repair.
06:00-08:59
Heart attack danger zone
Good time to wake up
Heart attacks more likely
Men have their testosterone peak
Be careful - this is the time of day your heart is most vulnerable. Blood vessels are stiffer and more rigid, the blood is thicker and stickier and your blood pressure is at its peak. It all adds up to the greatest risk of a heart attack you'll face today. Your body is kicking into gear as sleep hormone melatonin production stops. It is a poor time to exercise.
09:00-11:59
Mind most alert
Maximum cortisol levels
Maximum alertness
Best short-term memory
You're probably in work and it's time to get some of the heavy thinking done. The stress hormone cortisol reaches its natural peak giving our brains a boost of alertness. We tend to be most productive before lunch and tests show short-term memory is at its best. Stay busy, there's a big dip coming up.
12:00-14:59
Biological siesta
Increased gastric activity
Post lunchtime dip in alertness
Surge in road deaths
With a lunchtime belly full of food, there's a boost in gastric activity. But this soon adds to the 'biological siesta' as alertness dips and affects driving ability. There's a noticeable rise in the number of deaths on the roads from 14:00, particularly in older people. It's also a bad time to drink alcohol as it can make you more drowsy than at other times of the day.
15:00-17:59
Go exercise!
Best lung & cardiovascular performance
Core body temperature rising to its peak
Good time to exercise
Go get a sweat on! Body temperature increases in the late afternoon like a natural warm-up, the heart and lungs work better and muscles are 6% stronger than at their lowest point in the day. Some people have even tried using this 'athletic sweetspot' to increase their chances of breaking sporting world records.
18:00-20:59
Watch what you eat
Poor time to eat a big meal
Liver handles alcohol better
Intuitive thinking is better
Ready for dinner and maybe a drink? Well you might not want to leave it too late. Emerging evidence suggests the body changes the way it handles food as it gets closer to night-time. Eating big meals in the evening could increase the risk of obesity and diabetes. The liver is more able to deal with alcohol if you fancy a tipple.
21:00-23:59
Getting ready for sleep
Melatonin production building
Core body temperature dropping
Good time to go to sleep
Bedtime is fast approaching and the pineal gland in the brain is churning out the hormone melatonin to help you nod off. Core body temperature is falling and the internal body clock is saying it's time to swap the sofa for the duvet. It'll happen first if you're a morning or 'lark' type person, before hitting the 'owls' a bit later.
Take the Quiz
Are you a lark or an owl?
People often describe themselves as a "morning person" or an "evening person" depending on when they feel their best. Of these five groups, see which description suits you best. Extreme larks are the ultimate early bird - up and out of the door while others are struggling with the snooze button on their alarm clock. But they pay for it in the evening when they nod off early. Larks also prefer mornings. They are out of bed early and greet the new day with cheer and a smile while everyone else is grumpy, bleary-eyed and hugging a mug of coffee. Some people function only in the morning, while others hit their stride well after the sun has set, but the Balanced group is somewhere in the middle. It's a good place to be - the best of both worlds. Owls are no strangers to burning the midnight oil and love a late night. However, mornings are a struggle. Extreme Owls - no-one can power through the night quite like them. 4am? No sweat! But early starts must fill them with dread and they've probably worn out the snooze button on the alarm clock too.
