Energy & the brain

Tired All the Time? It Might Not Be Sleep.

Nearly ten thousand people a month in Britain type “tired all the time” into Google. Most of them are sleeping seven hours. We spent two years asking what the rest of the answer is.

There is a particular kind of tired that sleep doesn't fix.

You go to bed at a reasonable hour. You get your seven hours, more or less. And then within two hours of sitting down at your desk you are already looking for something — coffee, a biscuit, your phone — to get you the rest of the way to lunch. By three in the afternoon the day has gone soft at the edges. You read the same email four times. The word you want is there, and then it isn't.

The strange part is that you can't point at anything wrong. You're not ill. Your bloods came back normal. You slept.

So you assume it's you. Almost everybody does.

What people actually say

It isn't described as tiredness. It's described as weight.

We began paying attention to this because our own customers kept describing it in nearly identical language, unprompted, in reviews that were meant to be about a drink. Not slower. Heavier. Not that they couldn't do the work — that doing it cost more than it used to.

That phrase — without me having to force it — turned out to be the tell. What people were describing wasn't a loss of ability. It was a rise in the price of using it.

The measurement that doesn't match the feeling

Why the tests keep coming back normal

In March 2026, researchers published cognitive testing on 14,234 English women aged 45 to 55 — one of the largest datasets of its kind. If the felt experience of fog were a loss of capacity, it should have shown up. It barely did. The measured differences were a few hundredths of a standard deviation, and on some tasks the women reporting the worst symptoms scored marginally better.

Which sounds, at first, like the symptom is imaginary. It isn't. A Lancet review three weeks later resolved the paradox with a definition worth borrowing well beyond the group it was written about:

You can still do it. It just costs more than it used to. That is why the tests are normal and why nobody believes you, including, on the bad days, yourself.*

And it reframes the question. If the problem is cost rather than capability, then the thing to look at isn't your brain. It's the ledger it's running on.

* Cognitive testing in 14,234 English women aged 45–55: npj Women's Health, March 2026. The efficiency framing: Lancet Obstetrics, Gynaecology & Women's Health review, 13 April 2026.

The mechanism

Two lines, and the gap between them

Your brain uses around a fifth of your daily energy. Running it means a set of unglamorous jobs happening continuously: turning fuel into usable energy inside cells, building and clearing the chemicals that carry signals between them, keeping blood moving, repairing and protecting tissue as it goes. Every one of those jobs runs on specific nutrients, and a demanding day burns through them faster than a quiet one.

So there are two lines to track across a week. One is what's being asked of you — and for most people that line climbs from Monday. The other is what you're running on, which does not.

Read it that way and a lot of otherwise confusing things line up. Why the fog is worse late in the week than early. Why a holiday fixes it and a lie-in doesn't. Why it lifts on a Saturday when nothing about your brain has changed — only what's being asked of it.

What the gap is made of

A brain doesn't run out of energy. It runs out of the things that make energy usable.

It's worth being specific about what's actually running short, because "nutrients" on its own is the kind of word that means nothing.

Your brain is about two per cent of your body weight and takes roughly a fifth of your daily energy. It never switches off. And unlike muscle, it holds almost no reserve — there is no store it can draw down on a hard day and refill on an easy one.

What it burns isn't only calories. Turning fuel into usable energy inside a cell is a chain of reactions, and every link in that chain needs a specific cofactor to run: thiamine, vitamin B6, vitamin C, magnesium. The chemical messengers that carry signals between neurons are built from raw materials — tyrosine, choline, folate — and broken down again after use. The membranes those signals travel across are rebuilt continuously. And the harder the tissue works, the more oxidative wear it produces, which has a cost of its own to clear.

None of that is recycled. It is consumed, and it is replaced from what you ate.

Now put the two halves together. Consumption scales with demand — a week that asks more of you costs more of these than a quiet one. Intake doesn't. Your diet is a habit rather than a response: it is roughly the same on the Thursday of a brutal week as it was on a slow Sunday. Nobody eats more folate because the week got harder.

So the gap in that chart isn't a metaphor. It's a ledger, and it has line items.

What it looks like in the data

This isn't a metaphor. Some of it has already been counted.

The National Diet and Nutrition Survey is the government's rolling measurement of what Britain actually eats. Among other things, it reports how many people fall below the Lower Reference Nutrient Intake — the floor, the level below which intake is treated as inadequate for most people.

Take magnesium, which is one of the nutrients doing the most work in the paragraphs above. Across women aged 19 to 64, roughly one in nine sit below that floor. Among women in their twenties it is closer to one in five.†

On its own that is only a number. What makes it matter is the second half.

Put plainly: demanding periods are associated with losing more magnesium in urine — the body sheds more of it when it is under load. And low magnesium status has in turn been associated with reduced tolerance to further stress. The research is careful about how firmly it puts that, and so are we. But the shape of it is a loop, and it is a loop most people will recognise from the inside: a hard week costs you more of the thing that makes hard weeks manageable.

That is the sentence to sit with, because of what it doesn't say. Running short doesn't make you ill. It doesn't take a capability away from you. It lowers how much you can absorb before the day starts costing more than it used to.

Which is, almost word for word, the definition the Lancet review was reaching for.

Magnesium contributes to normal psychological function and to the normal functioning of the nervous system.

Magnesium is simply the clearest example, because it is the most studied. The same shape holds across the rest of the set — the cofactors that run cellular energy, the raw materials neurotransmitters are built from, the material membranes are rebuilt with. Turnover rises with demand. Intake doesn't move.

So the fog isn't imaginary, and it isn't a character flaw, and it isn't something a stronger coffee is going to reach. It is what a shortfall feels like from inside a brain that is still entirely capable — and is simply running the week on less than the week is charging.

† Proportion of women with magnesium intakes below the Lower Reference Nutrient Intake, from analyses of the National Diet and Nutrition Survey rolling programme: HSIS, Dietary Trends in the UK 20 Years On (2019) and Derbyshire, Frontiers in Nutrition (2018). Excretion under load and tolerance to stress: Cuciureanu & Vink, Magnesium in the Central Nervous System (2011) and Lopresti, Advances in Nutrition (2020).

The usual answers

Each of them moves one line

Everything sensible you have already tried works on part of this, which is why each of them helped a little and none of them finished the job. Sleep works on the repair side rather than the supply side — and if you are waking at two or three in the morning, which is when British adults most commonly do, the hours in bed are not the number that matters. Magnesium on its own is one line item out of a dozen. Turning off notifications genuinely helps, it is free, and almost nobody does it. And caffeine adds nothing to the ledger at all: it hides the reading. It blocks the signal that tells you you're tired while the tiredness accumulates underneath, and when it clears, all of it arrives at once. That is the three o'clock wall — and the obvious fix for a three o'clock wall is more caffeine, which takes it out of tonight, which takes it out of tomorrow.

Britain has quietly started working this out on its own.

And for a lot of women between about forty and fifty-five there is a hormonal transition sitting underneath all of it — which is worth a conversation with your GP before anything else, and worth saying plainly that a daily drink is not an alternative to HRT and we won't pretend otherwise.

What's left

Put back what the week draws down

Which leaves the unglamorous option. Not stimulation, and not one heroic dose of a single thing, but replacing the set of materials a demanding week runs down — every day, at amounts printed on the label, judged over weeks rather than in the first twenty minutes.

That is what Axolt is. One sachet in 300ml of water, once a day, after lunch, in the slot where you'd otherwise reach for the second coffee. Everything below is what's in it, and what each part of it is there to do.

Questions people ask us

Take in the morning or early afternoon rather than the evening. Food supplements are not a substitute for a varied and balanced diet or a healthy lifestyle. Not suitable if you are pregnant or breastfeeding. If you take prescribed medication, speak to your GP or pharmacist first.