9 Nov 2026 08:00
#159 - Why Thinking Makes You Tired
Why do you feel drained after sitting at a desk all day? Matt explores the unsettled science of mental fatigue. Popular ideas like running out of brain glucose are debunked. Instead of an empty fuel tank, the culprit may be a "full ashtray." Research links mental exhaustion to a build-up of glutamate in the prefrontal cortex. This byproduct makes thinking feel costly, explaining why we make impulsive, low-effort choices by 5 PM.
How do we combat this brain drain? Matt reveals that lack of sleep sabotages your motivation to think, not your capacity. To restore focus, real breaks are essential, while quick fixes like breakfast and hydration offer limited cognitive benefits for adults. Finally, we uncover the truth about coffee: your caffeine hit might just be curing withdrawal, not boosting your brain. Tune in to learn how to protect your mental stamina.
Please note that Matt is not a medical doctor, and none of the content in this podcast should be considered medical advice in any way, shape, or form, nor prescriptive in any way.
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As always, if you have thoughts or feedback you’d like to share, please reach out to Matt:
Matt: Instagram @drmattwalker, X @sleepdiplomat,
