Some people wake with the sunrise, full of energy and focus, feeling they have already completed half a day’s work before the world stirs. Others only begin to function in the evening, when the house is quiet and the phone stops ringing. For years, this difference was attributed to habits, self-discipline or “personality.” But research in recent years paints a far more complex and intriguing picture.
The difference between morning types and night types is not merely a matter of personal preference. It reflects a deep biological mechanism with genetic, physiological and even microbiological roots.
Larks and owls
Sleep researchers generally divide people into three main types:
- Morning types — sometimes called “larks”
- Night types — “owls”
- Intermediate types — the large majority of the population
Morning types tend to wake easily, feel alert and focused in the early hours and grow tired by evening. Night types, by contrast, struggle to rise early, experience a burst of energy later in the day or even at night and have difficulty falling asleep at an early hour. Most people fall somewhere in the middle, often with a slight lean toward the evening.
It’s not just in the brain — it’s also in the gut
One of the more intriguing findings in the field comes from an Israeli study that examined the link between sleep patterns, diet and gut bacteria. Researchers found that morning and night types differ in the composition of their microbiome — the population of bacteria in the digestive system.
Clear dietary differences were also identified: night types ate fewer fruits and vegetables, consumed fewer complex carbohydrates and were more likely to drink sugary beverages and eat fatty, meat-heavy foods.
The researchers’ conclusion was cautious but thought-provoking: changes in diet that affect gut bacteria may also influence sleep patterns — and perhaps even whether a person is more of a lark or an owl.
Chronotype: our personal internal clock
The scientific term for our preference for morning or evening is chronotype. It refers to our individual biological clock, which determines when we are most alert, creative and focused — and when it is best to leave us alone.
The body’s central clock is located in the brain, but clock mechanisms exist in nearly every cell. Under normal conditions, these clocks are synchronized. Research on the biological clock was awarded the Nobel Prize in physiology or medicine in 2017, underscoring its importance to human health.
Chronotype also has a clear genetic basis. Scientists can, for example, examine cells taken from a skin sample and measure gene expression over the course of a day to determine a person’s internal cycle. Still, most people are not extreme types. Estimates suggest that about 2 in 10 are clear evening types, while only 1 in 10 is a distinct morning type.
When society runs early, owls pay the price
Modern society is built around early schedules: work, school, institutions and services. For night types, this presents a daily challenge. They go to bed late but are required to wake early, leading to chronic sleep deprivation.
Studies show that night types face a higher risk of depression, obesity and diabetes. They may also experience more conflict in relationships, family life and the workplace — simply because they are not synchronized with the prevailing social rhythm.
Test yourself: which type are you?
You are likely a morning type if:
- You wake easily at sunrise, even without an alarm
- You are most productive in the morning
- You do not need coffee to start your day
- You experience an energy dip in the afternoon and evening
You are likely a night type if:
- You enjoy staying up past midnight
- You naturally wake around 9 or 10 a.m.
- Your day only “gets going” in the afternoon
- You reach peak concentration and creativity in the evening
And in between?
Most people — those who can function in both morning and evening, as long as they are not pushed too hard.
Can you change your chronotype?
The surprising answer is yes, to a certain extent. Chronotype is influenced by age, seasons, light exposure, geographic location and even our beliefs about sleep. One of the most powerful tools for shifting it is light exposure: bright light suppresses melatonin, the sleep hormone, and promotes alertness.
Tips for adjusting your biological clock
For morning types who tire too early:
- Take a walk or engage in light activity in the afternoon
- Schedule workouts for later in the day
- Plan social activities in the evening
For night types who want to wake earlier:
- Dim lights in the evening and avoid screens before bed
- Expose yourself to sunlight immediately upon waking
- Avoid sleeping in late on weekends
- Move exercise to the morning or early afternoon
- Limit caffeine to the morning hours
Ultimately, there is no “good” or “bad” type. There is only a personal biological clock — and sometimes it does not align with the social one. In recent years, there has been some movement in the right direction: eliminating zero-period classes in schools is an important step that acknowledges not all brains wake at the same hour. But change need not stop there. Workplaces can also reconsider flexible start times, assign tasks according to individual peak hours and adopt hybrid models that allow people to operate when their nervous system is at its best. Such adjustments are not indulgences — they are investments in health, productivity and quality of life.
The author is a healthy lifestyle researcher and holds a doctorate in gerontology.