Tuesday, 28 May 2024

Total Body Potassium (TBK)

Total Body Potassium (TBK) is a method used to measure body composition. This procedure accurately determines the body’s total cell mass, which represents the active growing tissues in the body. By estimating the fat-free or lean body mass, TBK can provide valuable insights into an individual’s overall health and fitness.

Understanding Total Body Potassium

The primary purpose of TBK is to measure total cell mass. This measurement involves the use of extremely sensitive equipment that measures the gamma rays emitted from the naturally occurring radioactive isotope of potassium known as 40K. By shielding the subject from environmental radiation and measuring the radiated 40K over a specific time period, TBK can be estimated.

Advantages and Disadvantages of TBK

One of the significant advantages of TBK is its relative simplicity and safety. Apart from the initial cost of the equipment, operational expenses are relatively small. However, it’s essential to note that the required instrument for TBK is expensive to install and has limited availability. As a result, TBK has mostly been replaced by newer, more accurate techniques for quantifying total-body fat.

Determining Body Composition

TBK relies on the fact that the proportion of total potassium found in human tissues as 40K is constant at 0.0118% of total potassium. By measuring 40K, it becomes possible to calculate total-body potassium. Since potassium is distributed mainly within the intracellular compartment of fat-free mass, the ratio of total-body potassium to fat-free mass can be used to determine fat-free mass and total-body fat.

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Q: Is TBK the most accurate method for measuring body composition?
A: While TBK has been widely used in the past, newer techniques such as Dual-Energy X-Ray Absorptiometry (DEXA), Near Infrared Interactance, and Magnetic Resonance Imaging (MRI) offer greater accuracy and reliability.

Q: Are there any alternative tests for measuring body composition?
A: Yes, there are alternative tests such as Total Body Electrical Conductivity (TOBEC), Computed Tomography (CT), and Total Body Protein (TBP) that provide different approaches to assessing body composition.


Total Body Potassium (TBK) is a method that provides valuable insights into an individual’s body composition. Although it has been largely replaced by newer techniques, understanding the principles behind TBK can help in appreciating the advancements in modern body composition analysis. To learn more about TBK and other body composition tests, visit Auralpressure.


  • Burmeister, W (1965), Potassium-40 Content as a Basis for the Calculation of Body Cell Mass in Man. Science 148, 1336-1337.
  • Rosin, R and Shulov, A (1961), Estimation of total body fat from potassium-40 content. Science 133, 1918.
  • Gilbert B. Forbes, James Gallup, and John B. Hursh, (1961) Estimation of Total Body Fat from Potassium-40 Content, Science 13, Vol. 133. no. 3446, pp.101-102.