Trial – Carbon IN, Carbon OUT

Oxygen consumption

Your resting oxygen consumption is your resting metabolic rate. This is the minimum amount of oxygen your body needs to stay alive and it depends on your age, gender and body composition.

The "gold standard" for determining your resting oxygen consumption is to measure it, however, unless you are a body-builder or have a metabolic disorder, the figure calculated by this page for a person of your age, weight, gender and height is very likely to be within plus or minus 10–15% of your true resting metabolic rate.

Your resting carbon dioxide production

The amount of carbon dioxide your body produces at rest depends on your resting oxygen consumption and on the ratio of carbohydrate to fat your cells are burning. This figure varies throughout the day.

When your cells are burning pure carbohydrates, the volume of carbon dioxide they produce is always exactly equal to the volume of oxygen they consume. When your cells are purely burning fat, however, the volume of carbon dioxide they produce is only 70% of the volume of oxygen they consume.

The difference is due to the different chemical composition of carbohydrates and fat, and it allows physiologists to determine the ratio of the mixture of fuel your body is burning at any given moment. Measuring your oxygen consumption and carbon dioxide production simultaneously, and then dividing your V̇CO₂ by your V̇O₂ gives a result called your respiratory quotient, R.Q.

If you consume a low-carbohydrate ketogenic diet, your respiratory quotient will be closer to 0.7 on average throughout the day. If you consume a mixed diet that includes carbohydrates, your respiratory quotient will be closer to 1 on average.

The calculator on this page uses an RQ of 0.85 for the standard diet, and RQ of 0.75 for the ketogenic diet to calculate your V̇CO₂. You will notice that your oxygen consumption remains the same when you change the type of diet you consume.