Its All About Carbon

Ruben Meerman is an Australian television science presenter who commonly performs science demonstrations for school kids. At a Tedx Talk in 2013, Ruben laid out what is probably one of the most profound ideas in the management of weight loss. The idea that weight loss is simply basic chemistry. While the initial presentation establishes the concept that fat is something we breath out in the form of carbon dioxide (CO2), more fundamental I found is a principle that weight management is about managing carbon.

So how much weight do we potentially lose each day just by simply breathing?

The answer to that is fairly complex if you are an elite athlete. However, for people like me with a BMI over 40, we can cheat a bit using general estimates.

Part I – VO2 and VCO2

To start you need to understand two concepts: VO2 and VCO2.

VO2 is the amount of oxygen you breathe in. VCO2 is the amount of CO2 you breathe out.

At rest, we create approximately 0.8 liters of CO2 for every liter of oxygen we breathe. So if we can determine our resting VO2, we can determine our VCO2.

For most people, your resting VO2 will be approximately 0.0035 l/kg/minute. During extreme exercise, this can increase by 10x or more.  We will only be concerned with our resting VO2 rate for now as this is going to help establish some baseline parameters for our fitness goals.

VO2/day = Resting VO2 (L/Kg/min) x Mass (Kg) x 1440 (min)

For a person weighing 100 kgs, your VO2/day = 0.0035 x 100 x 1440 = 504 L per day

To find your resting VCO2/day you simply multiply this number by 0.8.

VCO2/day = Resting VO2 /day x 0.8

For a person weighing 100 kgs, your VCO2/day = 504 L per day x 0.8 = 403 L per day

Part II – VCO2 to Fat

Now we need a little bit of grade 10 chemistry. To convert your VCO2 to how much fat you are exhaling each day, we need to convert your VCO2 to grams.

To do this we need to know two things: for any given gas at 1 atmosphere of pressure, there are 22.4 L per mole of that gas and 1 mole of CO2 weighs 44g.

The formula we need now then is

Mass of CO2 (g) = # of liters of CO2 / 22.4 L per mole x 44 g per mole

For a person weighing 100 kg, the mass of CO2 produced is therefore 403 / 22.4 x 44 = 792 g

According to Meerman, for every 10g of fat we “burn” we create 8.4g of CO2 and 1.6g (ml) of water.

This is also basic chemistry (formula ratios). If 8.4 g CO2 = 10 g fat then 792 g of CO2 = x.

A quick rearrangement gives 792 x 10 / 8.4 = 942 g of fat (2 lbs).


So what was the point of all this math stuff? It is basically this. Even if you slept all day and ate nothing, the maximum amount of fat a 100 kg person could lose is about 940 g per day. This would never actually be the case however as you very rarely metabolize only fat for energy. In fact, this type of a starvation diet tends to burn muscle before burning fat as the body is programmed to preserve fat stores when faced with extreme changes in diet. And coming off a diet like this the body tends to want to increase body fat rather than repairing muscle tissue.

Does this sound familiar? Taking off 20 lbs of weight just to put 25 lbs of weight back on again?

As part of the next few articles, we are going to look at different ways we can play with our VCO2 number and use it to our advantage.

Resetting the Clock

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