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A comment on When somebody loses weight, where does the fat go?. Parent comment

Re:When somebody loses weight, where does the fat go? by maxerickson on Monday November 27, 2017 @12:09PM (#15788912)
How much weight does a typical person breath out in a day though?

(if you figure ~2000 calories worth, it doesn't seem like the breathing weight out is so much the issue...)

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Re:When somebody loses weight, where does the fat go? by mikeash on Monday November 27, 2017 @12:42PM (#15789228)
According to the article, a typical person will breathe out about 200 grams of carbon per day. (The oxygen in the CO2 comes from oxygen you breathe in, so doesn't contribute to any net weight change.)

A pound of fat is about 3500 calories, and typical sedentary metabolic rate is about 2000 calories per day, so you'd expect to lose about 0.57lbs ~= 260 grams per day if you didn't eat. The article says that CO2 makes up 84% of weight lost (the rest is water), so that fits fairly closely to the 200 grams/day of CO2 breathed out.

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