The real reasons you feel more tired, hungrier, less motivated and emotionally flat when the seasons change — and why the answer might be simpler than you think.
Can I ask you something?
When did we all agree to feel exactly the same in every season?
Same energy in July as in January. Same appetite, same drive, same output, same body — regardless of whether the sun sets at 5pm or 8pm, regardless of whether we wake in pitch dark or in golden morning light.
Nobody signed up for that.
But somehow, that became the standard we hold ourselves to.
And every winter, when the body inevitably pushes back, we interpret it as failure.
I want to offer you a different interpretation. One that is grounded in nearly 30 years of clinical practice and a deep respect for what the human body is actually doing when the seasons change.
What you are feeling in winter is not failure.
It is biology.
And the moment that distinction lands, everything shifts.
Does Any of This Sound Familiar?
Let’s start here, because I want you to feel seen before we get into the science.
As the days shorten and the temperature drops, do you notice:
- A tiredness that sleep doesn’t seem to fix
- Cravings for warm, starchy, comforting food that feel almost impossible to argue with
- Motivation that has quietly packed up and left
- A flatness to your mood — not quite sadness, but a kind of grey
- Less desire to socialise, exercise, or push yourself
- A sense that you are a completely different person in summer versus winter
- Guilt about all of the above
If you are nodding, I want you to know — you are not alone, and you are not broken. You are simply experiencing the collision between your biology and a world that does not account for it.
And that collision has a very clear physiological explanation.
You Are a Seasonal Creature…
Here is the foundational truth that I think changes everything:
Your body was never designed to be the same in every season.
For most of human history, life moved with the seasons.
Summer brought longer days, more movement, more light, more activity, more exposure. Winter brought shorter days, earlier darkness, slower rhythms, more rest, more nourishment, more inward focus.
The body adapted to each, and behaviour followed accordingly. Those adaptations did not disappear when we built houses with central heating and lit our evenings with screens. They are running in you right now — in your hormones, your neurotransmitters, your sleep chemistry, your hunger signals, your circadian biology. Every day, your body is reading the environment and adjusting itself in response.
The problem is not your biology. The problem is that we have built a world that demands the same performance from you year-round — and then left you to wonder what is wrong when your body refuses to comply.
Nature does not produce the same thing in every season. Why would you be any different?
Light Is the Master Clock
Everything I am about to share flows from one central fact: light governs almost everything your body does.
Every cell in your body runs on a roughly 24-hour internal rhythm — a circadian clock that governs when you feel alert and when you feel sleepy, when your hormones rise and fall, when your digestion is most active, when your immune system is at its peak.
That clock is synchronised every single day by the light that enters your eyes and signals a small cluster of cells deep in the brain — the suprachiasmatic nucleus — which then orchestrates the rest of the body’s timing.
When the light changes, the clock shifts. And when the clock shifts, everything downstream shifts with it.
This is not a theory. It is well-documented physiology — and it has now been confirmed at scale.
A 2021 study published in npj Digital Medicine — a Nature journal — tracked more than 200 people continuously across all four seasons for over a year, using objective wearable sleep monitoring. The findings were clear: people slept longer in winter than in summer, woke later, and sleep duration steadily decreased as daylight hours grew. These patterns were not random individual variation. They were consistent, measurable, and biologically driven across the entire group.
An earlier laboratory study by Honma and colleagues isolated light as the variable by controlling temperature, humidity and social contact entirely. The result was the same: wake times were earlier in summer and later in winter, bedtimes followed the same pattern, and both the melatonin and body temperature rhythms shifted seasonally in alignment with the changing light.
I notice this in my own body every year.
In summer, I am awake at 4.30am — alert, ready, genuinely happy to begin the day before the rest of the world has stirred. In winter, my body wants to sleep until the sun has actually risen. Not because my character changes between seasons. Because my circadian system is responding honestly to the light it is — or is not — receiving.
That is not laziness. That is your biology working exactly as it should.
Melatonin: Why Winter Mornings Feel Like Wading Through Fog
Melatonin is your primary sleep hormone. It is produced by the pineal gland in the brain and released in response to darkness. When light arrives, melatonin is suppressed and you begin to wake. When darkness comes earlier and stays longer, melatonin rises sooner in the evening and takes longer to clear in the morning.
In winter, this means your body is physiologically primed for sleep longer into the morning than it is in summer. In a natural environment, behaviour would follow — a slower start, a quieter morning, a gentler entry into the day.
But you probably have an alarm. And a commute. And a full calendar that starts at the same time regardless of what the sun is doing.
So your body is being asked to perform at full capacity before it has received the biological instruction to do so. The light that suppresses morning melatonin and signals your brain to power up is arriving later — and you are being asked to be sharp, functional, and ready before that signal has landed.
That foggy, slow, not-quite-present feeling on winter mornings? That is not a caffeine deficiency. That is lingering melatonin — and the single most effective intervention is also the most overlooked one.
Getting outside within 30 minutes of waking — even on a cloudy day — is one of the most powerful things you can do in winter. Natural light is the signal your brain needs to turn melatonin off and start the day properly.
Even indirect daylight through cloud has significantly more lux — the unit of light intensity — than indoor lighting. Your eyes need real daylight, even briefly, to anchor your circadian rhythm and shift your body out of its night-time physiology.
Serotonin: The Mood Chemistry That Moves With the Light
Serotonin is one of your primary mood-regulating neurotransmitters. It is the chemistry behind feeling calm, capable, content, and emotionally steady. It is also, importantly, the precursor to melatonin — your body converts serotonin into melatonin as darkness falls.
Serotonin production is directly stimulated by light. When light exposure drops in winter, serotonin production drops with it.
That low-grade flatness. The emotional greyness that settles in for the colder months. The sense that your usual resilience has gone quiet. The irritability that arrives out of nowhere. The tears that sit closer to the surface than they do in summer.
These are neurochemical consequences of reduced light exposure. They are not signs that something is wrong with you as a person. They are predictable, physiological responses to a seasonal reduction in serotonin — and they are experienced to some degree by a significant portion of the population, whether or not they would ever describe themselves as having a mood problem.
There is another piece here that I find particularly important: around 90 percent of your serotonin is produced in the gut, not the brain. Which means that what you eat across winter directly affects your emotional chemistry and your ability to feel emotionally steady. The carbohydrate cravings that come with the colder months are, in part, your body’s attempt to boost serotonin through the fastest route available. More on that shortly.
Vitamin D: The Winter Deficiency Most People Don’t Know They Have
Vitamin D is one of those nutrients that almost everyone knows the name of and very few people genuinely understand — which means it is consistently underestimated and, in my clinical experience, consistently undertreated.
It is not really a vitamin. It functions as a hormone — one that regulates immune activity, modulates inflammation, supports thyroid function, influences mood and cognitive clarity, and plays a significant role in how efficiently the rest of your endocrine system operates.
It is produced in the skin in response to UV-B radiation from the sun. In winter, UV-B levels fall. Time outdoors shortens. Skin is covered. And Vitamin D production drops, often significantly — even in sunny climates like much of Australia, where people often assume they are getting enough.
Low Vitamin D is associated with increased susceptibility to respiratory illness, worsened mood and anxiety, poor sleep, persistent fatigue, reduced immune function, and a generalised sense of the body running below its capacity.
These are also, notably, the exact symptoms most people chalk up to “just winter.”
In nearly 30 years of clinical practice, I see Vitamin D insufficiency constantly — and I see it constantly managed to a level that avoids deficiency but does not support optimal function. These are very different things.
If you are struggling through winter and no one has looked at your Vitamin D properly, that is a worthwhile conversation to have.
The Comfort Food Pull: What Your Body Is Actually Asking For
Let’s talk about the food piece, because I think this is where the most unnecessary guilt accumulates in winter.
The pull towards warm, hearty, satisfying food when the temperature drops is not a willpower problem. It is not emotional eating in the negative sense. It is ancient biology that predates supermarkets, central heating, and the concept of a diet.
Carbohydrate intake drives a short-term rise in blood glucose, which triggers a brief insulin response — and with it, an increase in tryptophan crossing the blood-brain barrier. Tryptophan is the amino acid the body uses to manufacture serotonin. When serotonin is low — as it is in winter — the body reaches for the fastest way to raise it. Warm, starchy, sweet food is that mechanism.
At the same time, reduced light activates the hypothalamus to increase appetite and signal the body to store energy. This is an evolutionary adaptation: in the environment humans evolved in, winter meant the potential for scarcity. A body that laid down fuel reserves in the colder months was a body that survived.
Your body has not received the memo that the environment has changed. It is still running those programmes.
Your body is not betraying you in winter. It is trying to look after you — with tools that made perfect sense in a very different world.
The challenge is that the foods most easily reached for — refined carbohydrates, sugar, processed snacks — give a brief serotonin lift followed by a blood sugar drop that triggers another round of cravings. Each lap of that cycle tends to come with a layer of guilt that makes the whole thing feel worse.
What helps is redirecting rather than restricting……..Protein-rich meals, complex carbohydrates like sweet potato, oats, and lentils, tryptophan-containing foods paired with quality fats — these support the same biological need without the crash. They are also the foods that genuinely satisfy in winter: warming, nourishing, and deeply sustaining.
A Slower Body: Why Winter Changes Your Metabolism and Your Energy
If you feel like your engine is running at a lower speed in winter, that is not your imagination.
Thyroid function — which governs your metabolic rate — is influenced by both light and temperature. In cold conditions, the body makes a series of physiological adjustments designed to conserve core heat and reduce unnecessary energy expenditure. Metabolic rate subtly downregulates. The body becomes more conservative with its output.
Movement also drops naturally as evenings shorten and mornings arrive in darkness.
And movement is one of the primary drivers of metabolic rate, insulin sensitivity, mood, and energy. The reduction is often gradual enough that it doesn’t feel like a conscious choice — it is simply the path of least resistance in a body that is being guided by its biology to slow down.
None of this is pathological. All of it is seasonal.
The body in winter is not malfunctioning — it is doing what winter bodies have always done. The question is not how to override it, but how to work with it intelligently so you feel well across the whole season, not just the warmer half of the year.
Living to the Seasons: The Idea That Changes Everything
This is the part of the conversation I most want to have with you.
We have spent centuries disconnecting ourselves from the natural rhythms our bodies were built to follow.
We have extended our days with artificial light, equalised our temperatures with heating and cooling, eaten the same foods year-round regardless of what is actually in season, and held ourselves to the same standard of productivity regardless of whether it is the height of summer or the depths of winter.
And in doing all of that, we have lost something important — not just philosophically, but physiologically. We have created a mismatch between what our bodies are designed to do and what we are asking them to do.
And then we have wondered why so many of us feel chronically tired, seasonally low, and perpetually behind.
Living to the seasons is not a new concept. Traditional medicine systems — Ayurveda, Traditional Chinese Medicine, indigenous healing practices across every continent — have always oriented health around seasonal living.
Eat what grows now. Rest when it is dark. Move when the light is long. Let the body follow the rhythm of the world it lives in.
Modern physiology agrees. The research on circadian biology, light exposure, seasonal melatonin, gut-brain chemistry, and metabolic rhythms all points in the same direction: the body functions best when it is allowed to move with the season rather than against it.
Seasonal living is not a retreat from modern life. It is a return to the intelligence your body has always had.
In practice, this does not require a radical lifestyle overhaul. It requires a shift in how you interpret what your body is asking for — and a willingness to meet it there.
In winter, that looks like:
- Honouring the body’s need for more sleep without guilt — it is a physiological request, not a character flaw
- Getting outside early in the morning, even briefly, to anchor your circadian rhythm with natural light
- Eating seasonally — warming, nourishing foods that genuinely support your winter biochemistry
- Moving consistently and gently rather than forcing summer-level intensity
- Creating more rest and restoration in your evenings rather than pushing through them
- Reducing the pressure on yourself to perform at the same pace in every season
- Understanding what your body is actually doing — rather than fighting it because nobody explained it to you
And in summer, leaning into the longer days, the higher energy, the natural inclination toward activity and expansion.
That rhythm exists too. The point is not to make every season the same — it is to let each one be what it is.
The Body Knows. We Just Need to Learn to Listen Again.
If winter has started to feel like something to white-knuckle your way through rather than something to move with, I think this is worth sitting with.
Your tiredness is real. Your hunger is real. Your flatness is real. Your need for more rest and less output is real.
And all of it has a reason — a clear, physiological, seasonal reason that has nothing to do with your worth, your discipline, or your capacity as a person.
You are not struggling with winter. You are struggling with a culture that told you winter should look exactly like summer. That is a very different problem — and one you can actually do something about.
Give your body what the season is asking it to have. Rest more. Nourish deeply. Step outside into the morning light. Let the pace slow without deciding that slow means broken.
That is not giving up. That is the most intelligent thing you can do.
If you’d like support working out what your body actually needs this winter — and how to feel well across every season, not just the easy ones — I’d love to have that conversation with you.
Warmly,
Teressa,
Naturopath | Clinical Nutritionist | Biochemist
