Why You're Running on Empty — It's Not About Trying Harder

You've cut back on caffeine. You've tried the earlier bedtime, the supplements, the "just push through the afternoon slump" approach. You've done the things you're supposed to do, and somewhere in there you've started to wonder — quietly, guiltily — why you still feel like you're running on fumes by 3pm.

If that's you, I want you to hear something before we go any further: it's not a discipline problem. It's not that you haven't found the right routine yet. There's a physiological story underneath the tiredness that most of us were never taught, and once you see it, a lot of the exhaustion stops feeling like a personal failing.

What's Actually Happening in Your Cells

I've been sitting with a conversation between Steven Bartlett and Dr Martin Picard on The Diary Of A CEO — Picard is a mitochondrial psychobiologist and professor at Columbia University, where he directs the Mitochondrial Psychobiology Group. His work looks at how stress and lived experience physically change your mitochondria, the structures inside almost every cell in your body that produce cellular energy.

The framing he offers is simple, and it rearranges a lot of what we think we know about tiredness: mitochondria aren't just background machinery quietly making ATP. They're sensors. They respond to what's happening in your life — your stress, your relationships, your sense of safety — and they adjust how much energy is available to you accordingly.

That's worth sitting with. Your fatigue may not be a sign that something is wrong with you. It may be a very literal, very physiological report from your own cells about what they've had to prioritise.

The 60% Question

The episode description states something that stopped me mid-scroll: stress hormones can divert up to 60% of your daily cellular energy away from repair and maintenance, and toward short-term survival responses.

I want to be careful here — that figure comes from Picard's own framing of his research, and I haven't independently verified the exact percentage, so treat it as his research claim rather than an independently audited statistic. But the underlying mechanism is well established in the stress physiology literature. Bruce McEwen's foundational work on allostatic load described exactly this trade-off decades ago: the same hormonal mediators — glucocorticoids and catecholamines — that protect you in the short term become costly when the stress response doesn't switch off (McEwen, 1998). Picard and McEwen's more recent systematic review found that psychological stress reliably alters mitochondrial function, particularly in the brain, across the majority of studies examined (Picard & McEwen, 2018).

Put plainly: when your body is busy responding to stress, it is not equally available for digestion, immune defence, cellular repair, or the slow work of aging well. Something has to give. Usually, it's the maintenance work — the stuff that doesn't show up as an emergency today, but quietly becomes tomorrow's health problem.

Why This Isn't the Same as Burnout Culture

I want to distinguish this from the "just rest more" conversation, because I think that framing under-serves what's actually going on. This isn't about needing a holiday, or "self-care" in the bubble-bath sense. It's about a nervous system that has been asked, repeatedly, to treat ordinary life as an emergency — and a body that has been quietly reallocating its energy budget accordingly, for months or years.

| The exhaustion isn't a character flaw. It's a system that's been asked to defend itself for far too long, with far too little chance to stabilise.

I've written before about why 'regulation' as a concept has lost meaning in wellness spaces — this is part of why. You can't breathe your way out of a body that has been running an allostatic deficit for years. The techniques aren't wrong. They're just being asked to do a job that requires something slower and more structural first.

Acute Stress vs. Chronic Stress: Why the Difference Matters

Picard draws a distinction that I think is one of the more useful things in the whole conversation: acute stress — the kind that resolves — is not the enemy here. A body that can mobilise energy for a real challenge and then stand down afterwards is a healthy, adaptive system. The problem is stress that never gets the "stand down" signal. Chronic, unresolved activation is what depletes the energy reserves that should be going toward repair.

This tracks with what I see constantly in clinic. The clients who are the most depleted are rarely the ones facing a single acute crisis. They're the ones who've been in a low hum of unresolved activation for so long that their baseline has quietly shifted — and they've often stopped noticing, because it became normal.

What "Energy Resistance" Really Means

One of the more useful frames from the episode is the idea of energy resistance — friction between what you're doing day to day and what would actually restore you. It's a different way of naming something I talk about often with clients: scattered energy, spent on things that don't align with what your nervous system actually needs, compounds the depletion in a way that's separate from how "busy" you technically are.

Two people can have identical calendars. One is quietly restoring capacity throughout the day in small, congruent ways. The other is spending every hour in low-grade resistance — saying yes to things that cost more than they give back. Only one of those people will be running on empty by Thursday.

What This Means for the Way You Live

None of this is an argument for doing less, exactly. It's an argument for noticing where your energy is actually going, and asking whether your nervous system has had a genuine chance to come back down after it's been asked to go up. Some starting points I come back to often with clients:

— learning to notice your own early cues of activation, before you're deep in overwhelm — building small, repeatable moments of settledness across the day, not just reaching for recovery once you've already crashed — getting honest about which parts of your week are "acute and resolved" versus "chronic and unresolved" — treating rest as a legitimate biological input, not a reward you have to earn

I've written more about what's actually happening in your body when rest doesn't feel safe, if this is landing and you want to go deeper.

The exhaustion was never proof that you're not trying hard enough. It's proof that your body has been doing exactly what it's built to do, for longer than it was ever meant to sustain it. Ground first. Energy follows.

References

McEwen, B.S. (1998). Protective and Damaging Effects of Stress Mediators. New England Journal of Medicine, 338(3), 171–179.

Picard, M., & McEwen, B.S. (2018). Psychological Stress and Mitochondria: A Systematic Review. Psychosomatic Medicine, 80(2), 141–153.

Bartlett, S. (Host). (2026, July 2). The Mitochondria Doctor: This Reverses Gray Hair, Makes You Feel Young Again & Fixes Disease! [Audio podcast episode]. In The Diary Of A CEO.