# gaining weight by yawning

In my last post, I made a statement, “I’ve found that if you wait a few minutes, the act of waking up seems to add grams of weight as you breath in the morning air and absorb it.”

Given the sharp and unforgiving nature of my friends (good for them!), this was immediately questioned.

So, I did a bit of math.

The short outcome is that yes, you do gain more than 2.5 grams of weight by breathing in the morning.

the math:

oxygen saturation in blood is about 90% when asleep, 95-100% (let’s say 97.5%) when awake.

I have about 5 litres of blood.

35% of blood is haemoglobin, and there is about .1551 moles of haemoglobin per litre.
that’s 1.75 litres of haemoglobin (5*.35).
1.75*.1551 is about .27 moles of haemoglobin.

every molecule of haemoglobin can bind to 4 O2 molecules.
That’s 8 atoms of Oxygen

so if blood was 100% saturated, it would contain 2.16 moles of oxygen (8*.27).
that’s 34.56 grams of oxygen.

97.5% of 34.56g is 33.7g of oxygen in the blood when awake
90% of 34.56g is 31.1g of oxygen in the blood when asleep

So… you wake up, you weight your self, you yawn a few times (oxygenating the blood), and you gain more than 2.5g of weight.