Sleep pressure, gut health, fibre and un/helpful diagnoses

There's more to this than meets the eye

Jan 28, 2026

Over the last few weeks I’ve been thinking a lot about sleep – not from a science bro optimisation standpoint or as a virtue, but as something we’re biologically driven to attain.

“Sleep pressure” as we laid out in last week’s newsletter (linked above) is a biological process.

The longer we stay awake, the more adenosine accumulates in the brain, increasing the drive to sleep. When we sleep, that pressure is discharged. When we don’t, it compounds. This process doesn’t care about motivation, identity, or insight. It just runs.

What’s interesting is how often sleep is treated as optional context rather than foundational physiology – especially in conversations about attention, regulation, weight loss, and ADHD.

Recently, in the pursuit of experts to speak to about sleep pressure in more detail, I came across work linking sleep disruption to gut health, fibre intake and inflammation, and found it interesting not because it offers a neat fix – it doesn’t – but because it helps explain why so many people feel dysregulated before we even get to questions of diagnosis.

Gut microbiota and sleep

A large and growing body of research suggests that people with sleep disorders tend to share certain gut microbiota patterns.

A systematic review of dozens of studies found that sleep disorders are associated with a “gut microbiota signature,” including fewer butyrate-producing (anti-inflammatory) bacteria and more pro-inflammatory species.

More strikingly, experimental work has shown that when gut microbiota from people with insomnia are transferred to germ-free mice, those mice develop insomnia-like behaviours – an effect that can be partially reversed with butyrate supplementation. This strongly suggests a biological link between gut bacteria, inflammation, and sleep regulation, even if it doesn’t yet establish directionality.

What this does not show is that improving gut health will automatically fix sleep. These are associations and mechanistic clues, not prescriptions. But they do point to something important: sleep quality reflects the overall regulatory state of the body.

Fibre, magnesium and “better days”

Observational studies add another layer. One study in young adults found that on days when participants ate more fibre-rich fruits and vegetables, their sleep was less disrupted that night. Magnesium intake also predicted better sleep quality.

But, again, this doesn’t mean fibre causes better sleep.

It may be that higher-fibre days correlate with more structured routines, better meal timing, lower stress, or less late-night stimulation. Fibre might be part of the causal chain, or it might be a marker of a better-regulated day.

Either way, the implication is the same: sleep improves when background physiological load is lower.

Anti-inflammatory butyrate – produced when gut bacteria ferment dietary fibre – helps maintain gut barrier integrity and reduces low-grade inflammation. Chronic inflammation increases physiological arousal and stress signalling, which makes sleep lighter and more fragmented. Fibre doesn’t override sleep pressure but more of it seems to reduce the noise that makes this pressure harder to dissipate.

Where ADHD enters the picture

This matters because many traits commonly attributed to ADHD – impulsivity, poor follow-through, emotional reactivity, difficulty delaying gratification, chaotic eating, late-night scrolling (or what I might call “Monday to Tuesday”) – are also classic consequences of chronic sleep debt.

This isn’t metaphorical. Sleep deprivation impairs prefrontal control and increases reward-seeking behaviour. When sleep pressure is high, the brain prioritises short-term relief over long-term goals.

Sleep dysregulation is well-documented in people with ADHD, and meta-analyses confirm consistent differences in sleep patterns compared to non-ADHD controls.

More recent work has even begun to explore links between gut-derived metabolites and sleep characteristics in ADHD populations, suggesting another layer of complexity rather than a single explanatory mechanism.

None of this means ADHD “is just tiredness.”

It isn’t.

ADHD and autism are real, and diagnosis can be life-changing. Medication helps many people. But sleep debt will reliably magnify attention problems in anyone – diagnosed or not.

Which raises an uncomfortable ordering problem: if someone is chronically under-slept, overstimulated, inflamed, and under-recovered, what exactly are we diagnosing? A neurotype? Or a nervous system under sustained load?

Sometimes it’s both. But sleep debt always makes the picture worse.

Explanation versus intervention

I’ve written before about how explanation can quietly replace action – in ADHD & weight loss, Berlin & San Sebastián and Labels: for Them or for Us? Diagnosis can reduce shame, provide language, and open doors to support. All of that matters.

But diagnosis is not a plan.

What worries me is how easily responsibility seems to be outsourced.

Diagnosis becomes the thing that will explain everything. Gut health becomes the thing that will fix everything. Supplements, protocols, labels, communities. Meanwhile bedtime remains negotiable, phones stay lit, routines stay chaotic, and sleep pressure keeps climbing.

Sleep doesn’t respond to insight. You don’t discharge sleep pressure simply by understanding it. You discharge it by sleeping.

That doesn’t make sleep easy.

Modern environments are hostile to it. Trauma, anxiety, and neurodivergence can make nights genuinely difficult.

But difficulty isn’t exemption.

If diagnosis is delayed, ambiguous, or unavailable, life doesn’t pause. Attention still has to be scaffolded. Habits still have to be built. Load still has to be reduced. Fibre won’t save you. A label won’t either. But both might make it easier to do the unglamorous work that actually changes things.

A more useful question than “What’s wrong with me?” might be: “What am I carrying that makes everything feel harder than it needs to be?”

Sleep pressure seems to me to be the quietest answer.

And that’s it from me!

Much love and I’ll see yas in the next one
J x

Bit of silliness for you inspired by my first full week of teaching classes again:

Fitness & Thinking

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