This may help:

https://ieeexplore.ieee.org/abstract/document/7969709

Article Developing and Validating an Age-Independent Equation Using ...

Article Evaluation of the novel Tanita body-fat analyser to measure ...

https://www.nature.com/articles/1601744

Dear Anusha, I agree with Carole C Tranchant .

You should use equations for TBW developed for a specific population, and not from the equipment.

Here some references to help you:

DOI: 10.1046/j.1523-1755.2001.00741.x

DOI: 10.1046/j.1523-1755.1999.00532.x

DOI: 10.1016/j.clnu.2015.03.013

DOI: 10.1016/j.medengphy.2008.06.009.

There are 3 main principles for measuring body water:

With multiple frequencies (Multifrequency Devices).

With a single frequency, typically 50 kHz (Single Frequency Device).

This model Tanita BC545N is a single frequency at 50kHz.

There are many regression equations available in the literature for measuring total body water from the frequency at 50 kHz, and it is generally based on these publications that manufacturers design their own water formulas in the form of water. adapting to their device. I did not see any communication from Tanita about their body water formula. So I do not think they want to share it.

Logically their water formula (TBW) relies on : weight, height, sex and impedance (or resistance) at 50kHz.

This device gives as information on the hydration rate that the % relative to the weight of the person (W) is TBW / W * 100. This is not very interesting because the fatty tissue contains only very little water. People with high fat potential therefore always appear very under-hydrated.

Devices that give a % hydration of the FFM (mass excluding fat) are preferred by far : TBW / FFM * 100.