Whether you are an early or a late type is genetic. How to determine your chronotype, why fighting it makes you ill and how to build work, training, meals and sleep around your inner clock.
In short
- Chronotype is the genetically determined position of the inner clock; about 15 percent are pronounced early types, 20 percent late types.
- Social jet lag, the difference between weekday and weekend sleep, raises weight, blood sugar and depression.
- Light in the morning shifts the clock forward, light in the evening backward; that adjusts the rhythm by one to two hours.
- The best time for training, focused work and dinner depends on the chronotype.
What the chronotype is
The inner clock sits in the hypothalamus and runs slightly differently in each person: set early in larks, late in owls, most lie in between. That is largely genetic but changes with age: teenagers are natural late types, from 50 the clock moves forward. A late type who is supposed to be tired at 11 pm is like an early type who is supposed to go to bed at 2 am: it works, but it is not restful sleep.
Determining your type
The simplest method: on free days without an alarm and without alcohol, note when you fall asleep and wake up. The middle of that sleep period is the marker. If it lies before 3 am you are an early type, after 5 am a late type, in between a normal type. The Munich Chronotype Questionnaire does this in more detail.
Social jet lag
Whoever gets up at six on weekdays and at ten at the weekend lives with a jet lag of two time zones, every week. Studies link social jet lag with higher weight, worse blood sugar, more smoking and more depression. Late types are hit hardest because work and school start early. The solution is not to sacrifice the weekend but to adjust the weekdays: start later where possible, and pull the clock forward carefully with light.
Shifting the clock
Light is the time-giver. Bright light in the morning shifts the clock forward, bright light in the evening backward. A late type who wants to get tired earlier goes outside for 20 minutes right after getting up, keeps the evening dark and eats early. An early type who wants to stay awake longer does the opposite. One to two hours of shift are realistic, not four. Melatonin in a small dose in the early evening can help late types in addition.
Building the day around the clock
Focused work sits in the morning for larks, in the afternoon and evening for owls. Strength training is most effective for everyone in the late afternoon when body temperature and strength peak; owls should not place it too late. Dinner at 8 pm for late types, at 6 pm for early types. And the most important rule: the same wake-up time on all seven days, with at most one hour of deviation.
Try it
Sleep CalculatorWhen do you have to get up? The best bedtimes by 90-minute cycles, or the other way round: when you should wake up.Caffeine CalculatorCoffee, espresso, tea, cola, energy drink with time: how much caffeine is still in your blood at bedtime, as a curve.Intermittent Fasting PlannerChoose wake-up time and method: your eating window, the fasting phases and what happens in the body hour by hour.Frequently asked questions
Can I train myself into a lark?
Partly. With light, fixed times and early meals the clock shifts by one to two hours. An extreme late type will not become an early type, but a moderate one.
Is getting up early healthier?
No. Healthy is regularity and enough sleep. Late types who can follow their rhythm are as healthy as early types; fighting the clock is what makes you ill.
What about shift work?
Shift work is a permanent jet lag and a health risk. What helps: fixed shifts instead of rotating ones, bright light during the night shift, sunglasses on the way home, a dark bedroom in the day and a nap before the shift.
This article is general information and not medical advice. If you have symptoms or existing conditions, or before changing any medication, talk to your doctor.
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