Measuring a person's body fat composition is a more accurate method of measuring a person's fitness than a scale which only measures weight.

What exactly is body fat testing?

The body is comprised of fat free mass (muscle, bone, blood, organs, etc.) and fat (adipose tissue).  Body fat testing is the process of calculating the amount of fat in a person's body.  For instance, if a 150 lb. woman has 20% body fat, she has 120 lbs. of fat free mass and 30 lbs. of fat.  A certain amount of fat is essential for bodily functions, such as regulating body temperature, and cushioning and insulating organs and tissues.  Fat is also the main form of the body's storage of energy.

Men and women do not have the same essential body fat requirements.  The American Council on Exercise has created this classification table.

How do you measure body fat?

There are several methods to do so, each with benefits and drawbacks.

Hydrostatic weighing - an underwater test to measure body fat and lean body mass percentages based on the relative density of fat and lean tissue.  This is the gold standard, however, the equipment is very pricey so the cost for a client to have it performed is often steep.

Anthropometry - measurement and analysis of parts of the human body.  Examples are skinfold, girth, and body weight.  This is generally inexpensive, but for it to be accurate, it is imperative that the measurements are taken by a practiced and skilled user.

Body mass index - a relative measure of body height to body weight for determining degree of obesity.  BMI = weight (kg) / height (in meters squared).  This is obviously inexpensive but it does not account for differences in levels of physical activity (i.e. athlete versus a sedentary individual) or other factors.  For instance, a highly trained athlete may have a high BMI, according to this type of measurement.

Bioelectric impedance - sends a safe, low level electrical signal through the body and measures the resistance to the signal as it travels through the body.  The more muscle a person has, the more water their body can hold, and the quicker the current passes through it.  Each model requires that you enter your age, gender, and height.  Some units also include the activity level of the user.  More advanced models, like the one we use at Catalyst 4 Fitness, enable us to monitor weight, body fat percentage, muscle mass, bone mass, basal metabolic rate, and visceral fat.  Tracking these measurements are important because weight loss does not necessarily equate to fat loss, or improved overall fitness or health.