There are various methods for calculating body composition values. None of these alternatives are as accurate or reliable as a DEXA Scan, which actually measures your body composition with precision.
Height – Weight Tables:
This method was originally developed to establish recommended weight ranges based on mortality among large populations. The studies do not currently represent an accurate cross-section of the population and, therefore lack validity.
Body Mass Index (BMI):
BMI is a simple calculation that determines height to weight ratios. It is a widely accepted method of obesity, but is often quite misleading in its results. Guidelines do not distinguish for gender, ethnicity or age and do not distinguish obesity or leanness for individuals who are extremely muscular. For example, two people can have an elevated BMI reading and one can have normal levels of body fat and the other individual can have undesirable elevated levels of body fat.
Anthropometry (Skin-fold Measurements):
Generally speaking, skin-fold measurements are an inexpensive, easy, and portable method of body fat examination. However, results are very subjective as precision depends on the skill of the caliper technician, the site measured, and the quality of the calipers themselves.
Bioelectrical Impedance Analysis (BIA):
This method calculates body fat, fat free mass, hydration level, and other body composition values by passing a small electrical signal through the body. Impedance to the signal is greatest in fat tissue, while fat free mass allows it to pass much more easily. Hydration plays a large role in BIA calculations and levels outside the normal range can cause inaccurate results. Dehydration, which can be caused by:
- not drinking enough fluids
- drinking too much caffeine or alcohol
- exercising or eating before testing
- certain prescription drugs
- illness or a woman’s menstrual cycle
Dehydration often causes fat tissue to be overestimated by BIA.