In London, the sun is up for about 16 and a half hours on the longest day of the year. On the shortest day in December, it manages less than eight. Further north, in Scotland or Scandinavia, the gap is even bigger. Your body notices this difference long before you consciously do.
Maybe you’ve felt it already this autumn. The alarm feels harder. The afternoon slump comes earlier. By 7 p.m. you’re on the sofa wondering why you’re so tired when you haven’t done anything unusual. You’re not imagining it, and you’re not lazy. Shorter days really do change how your body runs, and once you understand how, there’s a lot you can do about it.
What changes inside you when the days get shorter
Three things shift at the same time in late autumn, and together they explain most of that heavy, slow feeling.
Your melatonin runs longer. Melatonin is the hormone that tells your body it’s night-time. Darkness switches it on and bright light switches it off. When the mornings are dark, melatonin can hang around longer after you wake up, which is part of why getting out of bed in November feels so much harder than in June. The National Institute of Mental Health notes that people who are strongly affected by winter tend to produce too much melatonin, which increases sleepiness.
You get far less light. This is the part most people underestimate. Even a grey winter day outdoors is usually several times brighter than a well-lit office or living room. Indoor lighting often sits at only a few hundred lux, while daylight outside can reach thousands even when it’s cloudy. In summer you pick up plenty of bright light without trying. In winter you can easily go from a dark morning to an indoor desk to a dark evening without ever getting a proper dose.
Your routine shrinks. Fewer walks, fewer evenings outside, more time on the sofa, more comfort food. Each of these makes sense on its own, but together they lower your energy further. Less movement makes you feel more tired, which makes you move even less.
There’s also vitamin D. Your skin makes it from sunlight, and in much of Europe and North America the winter sun is too weak for that between roughly October and March. Low vitamin D is common in winter, though it’s only one piece of the puzzle. Our guide to vitamin D and energy explains who’s most likely to be low and when a blood test makes sense.
Normal winter tiredness or something more?
For most people, the seasonal dip is mild. You feel a bit slower, sleep a little more and crave heavier food, but you still enjoy things and get through your week. For some people, though, it’s much stronger. That’s called seasonal affective disorder, or SAD, and it’s a form of depression that returns at the same time every year.
| Usual winter dip | Signs it may be more (talk to a doctor) |
|---|---|
| A bit more tired than usual | Exhausted most of the day, almost every day |
| Sleeping slightly longer | Sleeping much more and still not feeling rested |
| Fancying warmer, heavier food | Strong carb cravings and noticeable weight gain |
| Staying in a bit more | Withdrawing from friends, losing interest in things you enjoy |
| Still feeling like yourself | Low, hopeless or numb for weeks at a time |
The NIMH describes winter-pattern SAD as often coming with oversleeping, overeating with carbohydrate cravings, and social withdrawal that can feel like “hibernating.” It’s more common in people who live further from the equator and in women. If the right-hand column sounds like you, please don’t try to push through it alone. SAD is well recognised and treatable, and a doctor can help.
The light gap, and how to close it
If there’s one thing to take from this article, it’s this: light is the strongest lever you have for winter energy. Not supplements, not coffee, not willpower. Light.
The timing matters as much as the amount. Bright light in the first hour or two after waking sets your body clock, switches off melatonin and tells your brain that the day has started. That’s why a 20-minute walk at 8 a.m. can do more for your energy than an hour outside at 4 p.m. We explain the science in more detail in our guide to morning sunlight.
In practice, closing the light gap looks like this. Walk or cycle part of your commute, even if it means getting off the bus one stop early. Have your morning coffee by the brightest window in your home, not in a dim kitchen. If you work from home, put your desk as close to a window as you can. Take your lunch break outside, even on cloudy days, because a grey sky still gives you far more light than any room. And at the weekend, plan at least one longer stretch outdoors while it’s light.
If your job keeps you indoors from dark to dark, you’ll have to be more deliberate. Treat a daylight break like a meeting that goes in your calendar: ten minutes outside before your first task, and another ten after lunch. Some people also find a dawn-simulator alarm helpful. It brightens the room gradually before your alarm goes off, so you don’t wake up in total darkness. It’s not a replacement for real daylight, but it can make dark mornings feel less brutal.
None of this feels dramatic, and that’s the point. Small daily doses of daylight add up over a winter in a way that a single sunny holiday never will.
About light boxes
Light therapy boxes give off very bright light (around 10,000 lux) and are a proven treatment for SAD. Mayo Clinic suggests using one for about 20–30 minutes within the first hour after waking, sitting roughly 40–60 cm away, with your eyes open but not staring into it. Choose one that filters out UV light. If you have an eye condition or bipolar disorder, speak to a doctor first.
A simple winter energy routine
You don’t need to overhaul your life for the next five months. A few steady habits, done most days, make a noticeable difference. Here’s the order we’d build them in.
1. Fix your wake-up time. Get up at roughly the same time every day, including weekends. It’s tempting to sleep in when it’s dark, but a moving wake-up time confuses your body clock and makes mornings even harder. After the clocks go back, this matters even more, as we explain in our guide to adjusting your sleep when the clocks change.
2. Get light in the first hour. Open the curtains straight away and switch on bright lights. Then get outside for at least 10 to 20 minutes before mid-morning, even if it’s just a walk around the block.
3. Move every day, ideally outdoors. Exercise is one of the most reliable ways to lift both mood and energy, and doing it outside gives you light at the same time. It doesn’t have to be a workout. A brisk walk counts. Here’s why walking is so underrated, and how exercise boosts your mood.
4. Eat for steady energy, not just comfort. Winter cravings for bread, pasta and sweets are real, and you don’t have to fight them completely. But pairing carbs with protein and vegetables keeps your energy from crashing an hour later. Our guide to eating for steady energy keeps it simple.
5. Keep your evenings dimmer. This might sound odd after all that talk about light, but it fits. Bright light in the morning and softer light in the evening gives your body a clear day-night signal. Lower the lights and put screens down for the last hour before bed.
6. Don’t drop your social life. It’s easy to cancel plans when it’s cold and dark at five. But seeing people is one of the best protections against the winter slump. Even a short coffee with a friend counts.
What about sleeping more?
Many people sleep a little longer in winter, and that’s usually fine. If you naturally need an extra 20 or 30 minutes, take it by going to bed earlier rather than sleeping in, so your wake-up time stays the same.
What doesn’t help is sleeping much longer and hoping the tiredness goes away. Very long sleep often leaves you feeling groggier, not better, and lying in bed in a dark room keeps melatonin running. If you’re regularly sleeping nine hours or more and still feel exhausted, that’s worth looking into. Our article on how much sleep you really need is a good place to start.
The coffee question
When you feel slow, the obvious answer is more coffee. A cup in the morning is fine, and it can genuinely help you get going. The problem is the third and fourth cup in the afternoon, which can push your bedtime later, shorten your sleep and leave you more tired the next day. In winter, when your sleep is already under pressure, it’s worth keeping caffeine to the morning and swapping the afternoon cup for a short walk outside. You get a lift either way, and only one of them costs you sleep.
When to talk to someone
Please speak to a doctor if your low mood or tiredness lasts most days for more than two weeks, if it’s affecting your work or relationships, or if you’ve noticed the same pattern every autumn for several years. Tiredness can also have causes that have nothing to do with the season, such as low iron, thyroid problems or poor sleep quality, and a few simple tests can rule these out.
And if you ever feel hopeless or have thoughts of harming yourself, contact a doctor, a local helpline or emergency services straight away. You don’t need to wait for things to get worse to ask for help.
The bottom line
Feeling more tired as the days get shorter is a normal response to less light, a longer melatonin signal and a routine that shrinks with the daylight. You can’t change the season, but you can change how much light you get, when you get it and how much you move. Start with the mornings: wake at the same time, let the light in, and get outside early. Give it two weeks before you judge it. Most people find that winter feels noticeably lighter, even when the sky outside doesn’t.
General information, not medical advice. If you think you may have seasonal affective disorder or feel low for more than two weeks, please speak with a qualified healthcare professional.