How mental load influences cortisol rhythm, blood sugar and nervous system tone
It is 10 o’clock at night. You have finally sat down. And your brain, apparently, has other plans.
You are replaying a conversation from three days ago. You are thinking about tomorrow, and the week after, and whether you replied to that message from last Thursday. You are solving a problem that has not even happened yet while still turning over one that is already done and dusted.
Sound familiar?
Here is what I want you to know: this is not a personality flaw. It is not a sign that you are anxious or that you need to try harder to switch off. What is actually happening is that your body is running a very real, very measurable stress response — every single time your mind stays in that loop. And over time, that has consequences that go well beyond feeling tired.
Women carry a lot. And I mean a lot.
There is a term for what you are doing — cognitive load. It basically means the mental tracking that never fully stops. Not just the doing, but the remembering, the planning, the anticipating, the worrying, and the replaying.
Most of the women I see are holding all of this at once:
- What happened earlier today that still does not sit right
- What needs to happen before the end of the week
- That thing from last month they still have not dealt with
- Something coming up in a few weeks that keeps nagging at them
- How everyone around them is doing and whether they are okay
That is the past, the present, and the future all running simultaneously. It is exhausting just to write it out.
This is not overthinking because something is wrong with you. This is what happens when a woman has been carrying responsibility — for herself, for others, for everything — for a very long time. The nervous system learns to stay on. And staying on has a cost.
Your brain does not know the difference between a real problem and a thought
This is the thing that surprises most of my clients when I explain it, so I want to be really clear here.
When you are lying in bed replaying a difficult conversation, or mentally running through your to-do list at 11pm, or worrying about something that may or may not happen — your body responds as if there is an actual threat in front of you. It cannot tell the difference. It just gets the signal: something is wrong, stay alert.
So it does what it always does when it thinks you are in danger. It triggers a stress response. Hormones are released, your nervous system shifts into high gear, your body starts preparing to deal with whatever is coming.
The problem is — nothing is coming. There is no threat to respond to and no action to take. But your body has already hit go.
In small doses, that response is completely normal and healthy. The issue is when it keeps happening, day after day, because the mental load never really clears.
What this does to your cortisol over time
Cortisol gets a bad reputation but it is actually essential. In the morning it helps you get up and get moving. It gives you focus, energy and drive. It is supposed to gradually taper off through the day so that by the time evening comes, your body can wind down, rest and repair.
That rhythm matters enormously. When it works the way it should, you feel energised in the morning, reasonably steady through the day, and naturally tired by night.
But when your brain is running a low-grade stress response most of the time, that rhythm gets knocked around. What I commonly see is:
- Cortisol still elevated at night, so the mind keeps going when it should be quietening
- Waking at 2 or 3am, often with that racing heart or spinning mind
- Waking in the morning already exhausted, as if sleep did not do much
- That flat, blunted feeling through the day — not exactly anxious, just never quite right
Over time the body tries to compensate, and that compensation creates its own problems. Tired but wired is probably the phrase I use most often in clinic. You are exhausted but you cannot fully rest. You are switched on but nothing feels sharp. Your body is caught between two states and not quite in either.
And here is where blood sugar comes in
This is the piece I do not think gets talked about enough, so bear with me because it genuinely explains a lot.
One of cortisol’s jobs — going back to our days of actually running from threats — is to push glucose into the bloodstream quickly so the body has fuel to respond. Every time a stress response kicks in, including the mental kind, that process happens.
Which means if your nervous system has been activated all day by a busy mind, your blood sugar has been getting nudged around all day too.
And then you wonder why, by three in the afternoon, you are absolutely desperate for something sweet. Or why you feel shaky and foggy before meals even when you ate not that long ago. Or why you wake in the early hours and cannot get back to sleep, sometimes with that slightly wired, slightly unsettled feeling.
These are not random. They are connected. And the connection often starts much earlier in the day than you would think.
Your afternoon crash, your cravings, your erratic energy — these may have far less to do with what you are eating and far more to do with what your nervous system has been carrying since you opened your eyes.
The nervous system that never gets to rest
Think of your nervous system as having two modes. One is your alert, action mode — the one that gets things done, responds to demands, keeps you moving. The other is your rest and repair mode — the one that digests your food properly, helps you sleep deeply, balances your hormones and lets your body actually recover.
You need both. You are designed to move between them throughout the day.
The problem with chronic mental load is that the alert mode never quite switches off. It does not have to be full-blown stress. It can be low and quiet — just a constant hum of alert-ness running in the background. Like driving with one foot always lightly on the accelerator. You are not flooring it. But you are never fully off either.
When the body stays in that state, some things quietly start to suffer:
- Digestion slows down, which is why bloating and gut symptoms often get worse when life gets busy
- Hormones get deprioritised — the body consistently puts stress hormones first when it feels under pressure, which means other things get less
- Inflammation can creep up over time
- Recovery from exercise takes longer because the repair work happens in rest mode, and rest mode is not getting much time
This is why so many women tell me they are doing everything right — eating well, exercising, trying to sleep — and still not feeling better. The missing piece is often not what they are doing. It is what their nervous system has never been given permission to put down.
This is not about doing less
I am not going to tell you to think less or worry less. The women I work with are not overthinking because they are fragile or neurotic. They are carrying real things — real jobs, real families, real health concerns, real pressure. That is not something to dismiss.
What I am saying is that the body does not factor in your reasons. It responds to the signal it receives. And a nervous system that is chronically activated will create downstream consequences regardless of why it is activated.
Once you understand that — once you can see the thread between the way your mind has been running and the way your body has been responding — the symptoms stop feeling like random bad luck. They start to make sense. And things that make sense can be addressed properly.
Your body is not failing you. It is doing exactly what a body does when it has been living in a state of sustained pressure. The question is just: what does it need in order to shift?
What I look at in clinic
When I work with a client who is presenting with fatigue, poor sleep, blood sugar swings, hormonal disruption or just that general feeling of running on empty — looking at how the stress response system is functioning is always part of the picture.
Sometimes it is the central piece. And when we address it properly, the things that felt stuck often start to move.
If you recognised yourself reading this — the exhaustion that sleep does not fix, the cravings, the waking at 3am, the sense of doing everything right and still not quite getting there — I want you to know that is not just how it has to be.
There is usually a reason. And when we find it, everything else starts to make a lot more sense.
Warmly,
Teressa,
Naturopath | Clinical Nutritionist | Biochemist
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