Respiratory exchange ratio

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Respiratory Exchange Ratio (RER) is a dimensionless number used in calculations of basal metabolic rate (BMR) when estimated from carbon dioxide production. It is calculated from the ratio of carbon dioxide produced by the body to oxygen consumed by the body. Such measurements, like many other biometric measurements, are usually made under a strict set of conditions.

Overview[edit | edit source]

The respiratory exchange ratio (RER) is a measure used in physiology, exercise physiology, and nutrition to estimate the composition of the fuel mix (fat, carbohydrate, and protein) being metabolically catabolized to produce energy. It is calculated by taking the ratio of the volume of carbon dioxide (CO2) produced over the volume of oxygen (O2) consumed.

Calculation[edit | edit source]

The RER is calculated using the following formula:

RER = VCO2 / VO2

Where:

  • VCO2 is the volume of carbon dioxide produced
  • VO2 is the volume of oxygen consumed

Interpretation[edit | edit source]

An RER of 0.70 indicates that fat is the predominant fuel source, a value of 1.00 is indicative of carbohydrate being the predominant fuel source, and values between 0.70 and 1.00 suggest a mix of fat and carbohydrate. Values above 1.00 can occur during intense exercise and suggest a high rate of glycolysis.

Clinical significance[edit | edit source]

RER values can be used in clinical settings to estimate a patient's metabolic rate or to design a weight loss program. It can also be used in exercise testing to determine an individual's anaerobic threshold and to monitor the intensity of exercise.

See also[edit | edit source]

Template:Physiology-stub Template:Exercise-stub

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Contributors: Prab R. Tumpati, MD