Why You Lose Weight While You Sleep

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

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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.

Over the course of the night, through respiration, you lose a pound of weight to the carbon atoms in Carbon Dioxide.