Entertainment | Science

Every Night You Lose More Than A Pound While You're Asleep (For The Oddest Reason)

NPR | June 24, 2013 7:21 a.m.

Contributed By:

Robert Krulwich

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Here’s a simple question: Why do you weigh more when you go to sleep than when you wake up? Because you do. In the video below, you’ll see the evidence. You can check this yourself. Somehow, while doing absolutely nothing all night but sleep, you will wake up lighter.

This is not about bathroom stuff. If you awaken and weigh yourself even before going to the toilet, you will still be lighter than when you went to bed. Why?

Where Does The Weight Go?

My first thought was “sweat.” Maybe you sweat when you sleep, so some of your water weight disappears as water vapor. Turns out, that’s true. That’s part of the explanation — but not the fascinating part.

Derek Muller, a physics teacher in Perth, Australia, and host of one of my favorite science blogs, Veritasium, came up with the full answer, and it’s so surprising, so simple, it feels like one of those No Fuss, No Muss, Miracle Cures they talk about on late night television.

This is like the Sting song, “Every breath you take … ” All night long, every time you breathe out, a bunch of carbon atoms, formerly inside your body, leave your insides and take off into the night air. You breathe in oxygen, O2. You breathe out carbon dioxide, (two oxygen atoms with a carbon atom attached), so there’s an extra carbon atom leaving in every round trip.

Each of those carbon atoms weighs almost nothing, a fraction of a fraction of a gram. But every breath expels roughly 10,000,000,000,000,000,000,000,000,000,000, or ten billion trillion atoms, so add up all the atoms coming from all the breaths you take all night long … and — could it be this simple? — you wake up carbon-depleted, more than a pound lighter.

Amazing.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

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