Your brain runs on twenty watts

Why do we talk about the brain like it's a computer when it's actually more like a very picky sports car?

Hannah Critchlow's piece in Aeon made me realize I've been thinking about mental fatigue all wrong. She points out that "the brain consumes around 20% of our total energy budget" despite being only 2% of our body weight. That's not a computer specification. That's a biological fact with real consequences.

It burns through glucose and oxygen at a rate that would make a Formula 1 engine jealous.

This changes how I think about reading, honestly. When I hit that wall around page 200 of a dense book, that's not laziness or lack of focus. That's my brain running low on fuel. The mental effort of parsing complex sentences and holding multiple ideas in working memory has actual metabolic costs.

I keep thinking about how Kristin Hannah writes those long, emotionally demanding scenes in "The Great Alone." There's a section where Leni watches her father's PTSD spiral into violence during the endless Alaskan winter. Reading it feels exhausting in a way that goes beyond the emotional content. Your brain is working overtime to track the psychological dynamics, the environmental details, the building tension.

Critchlow suggests we need to respect these bioenergetic limits instead of trying to hack around them.

I'm not sure this holds up completely, but maybe our obsession with productivity apps and focus techniques misses the point. You can't optimize your way around biology. Your brain needs glucose, oxygen, and rest the same way your muscles do.

The weirdest part? We already know this about physical performance. No athlete tries to run a marathon on willpower alone. But we expect our brains to operate at peak capacity for 12-hour stretches fueled by coffee and determination.

Maybe it's about treating your brain like the energy-hungry organ it actually is.

Though I still don't know what to do with that information when I have 300 pages left to read.