Bioimpedance Analysis


first-line-therapy Bioimpedance Analysis, aka Bioelectrical Impedance Analysis, and Body Composition Analysis is the clinical assessment of tissue and fluid compartments in the body. They have proven very useful measures in preventive, therapeutic, and research applications. They do not diagnose or treat disease. Research has shown that body composition correlates directly to a continuum of health ranging from mortality and morbidity to immunity, longevity, high function, and high performance.

I have included descriptions of most of the measurements below but there are only a few that we will really focus on. They are Phase Angle, Fat Mass, Base Metabolic Rate, and Total Body Water (TBW) /Lean Body Mass.

Explanation of Measurement Results

Here are explanations for the measurements. Normal values are shown in biathe chart below.

Phase Angle

Phase angle is an indicator of cellular health. Phase angle values range from 3 to 15. Typical values for average healthy adults are between 6 and 8. A low phase angle is consistent with the inability of cells to store energy and indicate a breakdown in the selective permeability of cell membranes. Very high phase angles are usually found only in elite athletes.

Body Capacitance

Body capacitance is the absolute amount of energy storage of the body due to intact cellular membranes. That is, this number is proportional to the number of cells and to the integrity of the cellular membranes. Values range from 200 to 1500 picofarads, with normal values ranges from 500 to 1000 pF.

Resistance and Reactance

These readings are intermediate results used to calculate other measurements. Their exact values are not of much use to us in this class.

Body Cell Mass (BCM)

BVM is the mass of all of the metabolically active parts of your body – your living cells (muscle cells, organ cells, blood cells, immune cells, and the living portion of fat cells but not the stored lipids). It includes the intracellular water. Your specific BCM value is not relevant. What is important is the ECM/BCM Ratio.

Extracellular Mass (ECM)

ECM is the metabolically inactive parts of the body (bone minerals, blood plasma, and extracellular water). Your specific ECM value is not relevant to us. What is important is the ECM/BCM Ratio.

Lean Body Mass AKA Fat-Free Mass

Lean Body Mass includes all non-fat parts of the body, including all the body’s water and all metabolically active tissue and bone. Lean Body Mass is further divided into BCM and ECM.

Fat Mass

Fat mass is the total amount of stored fats in the body, including subcutaneous fat and visceral fat. The “ideal” fat mass depends on age and gender. There are numerous opinions out as to what ideal numbers should be. The American Council on Exercise recommends average men be under 25%, fit men under 18%, average women under 32% and fit women under 25%.

NOTE: If your TBW/Lean Body Mass is below 69%, your Fat Mass reading is inaccurately high.

Subtract 1% from your Fat Mass if your TBW/Lean Body Mass is between 68% and 69%.

Subtract 2% from your Fat Mass if your TBW/Lean Body Mass is between 67% and 68%.

Subtract 3% from your Fat Mass if your TBW/Lean Body Mass is between 66% and 67%.

Subtract 4% from your Fat Mass if your TBW/Lean Body Mass is below 66%.


Normal values would be approximately 1, indicating a 50/50 split between cellular mass and extracellular mass.

Body Mass Index (BMI)

BMI is a measure of a person’s weight relative to their height. This is a controversial indicator because it does not take frame size into account.

Basal Metabolic Rate (BMR)

The number of calories consumed and metabolized at a normal resting state over a 24 hour period. For a typical person, more than 90% of their calories are burned while at this normal resting state.

Intracellular Water

A measure of the amount of water contained within your cells. As a general rule 2/3 of your total water should be inside the cells.

Extracellular Water

A measure of the amount of water contained outside your cells. As a general rule 1/3 of your total water should be outside the cells.

Total Body Water (TBW)

The total amount of intracellular and extracellular water. Actual values are not of significant interest to us.

TBW/Lean Body Mass

This is the total of Lean Body Mass that is water. For an adult body water is expected to be 69% to 74% of lean body mass. If your number is under 69% you are dehydrated. If you didn’t drink 16 to 32 ounces of water a few hours before this test, this number on your BIA results may be 1% to 2% higher than normal.

TBW/Total Weight

The percentage of total weight that is water. Females should be around 55%, and males should be around 60%.

Normal Reference Values

Note: The top half are the reference values for men and the bottom half are the values for women

Bioimpedance Analysis (BIA) Reference Values
Bioimpedance Analysis (BIA) Reference Values