Body Fat Analysis

A personal trainer will sometimes use a body fat analysis test on a client to indicate general health. Research has shown that people with a higher body fat percentage have an increased risk of developing conditions such as obesity and diabetes, as well as heart disease and certain cancers, especially if they are storing excess visceral fats around the major organs.

By analysing body mass, a personal trainer can calculate how much of a client’s weight is fat mass and how much is non-fat mass, such as muscle, tendon and ligament.

The gold standard for body fat analysis is a Dual-energy X-ray Absorption (DEXA) machine, which analyses both bone density and body fat percentage. However, because DEXA machines are expensive, they are usually only found in hospitals or universities.

As most fitness trainers won’t have access to a DEXA machine, the alternatives are monitors that measure bioelectrical impedance or skin callipers. Both methods are based on regression formulas from the DEXA machine.

Recommended fat percentages

Because of their genetic make-up, women naturally have a higher level of body fat than men. The recommended ranges are:

Men: 6%-25%, ideally between 14-17% body fat

Women: 14-30%, ideally 21-25% body fat

If a fitness trainer has a client with percentages below or above these levels, they will require special attention.

Bioelectrical impedance

This involves sending an electrical impulse through the body to measure how much resistance it meets from body fat. The two ways of delivering the electrical impulse are:

1. A hand-held monitor, which measures upper-body fat percentages by sending an impulse from one hand-held electrode to another. As this instrument explicitly targets the upper body, it’s helpful in measuring the amount of fat located around the major organs.
2. A body composition monitor resembling scales, on which the client will stand as the electrodes send an electrical impulse through their body.

As these monitors rely on the time it takes for the electrical impulse to travel through the body, the fitness instructor should ask for the client’s height and age and factor them in.

The disadvantage of these methods is that there can be some measurement discrepancies. For example, if the personal trainer’s client is dehydrated, the poor conductivity of water can result in a lower reading than when the client is fully hydrated. Human and computer error can also be factors.

Skin callipers

A more effective way for a fitness instructor to measure a client’s body fat percentage is to use skin callipers. Measurements are taken from skin folds around the client’s body, added up, and then cross-referenced with a recognised graph, which will give a fat percentage depending on the person’s age. Skin calliper tests tend to be done on four, seven, or nine points around the body.

The four-point skin calliper test

The four-point skin calliper test focuses on the upper body, which is dangerous for fat, as it can gather around the major organs. The four sites where measurements are taken are the biceps, the triceps, the subscapularis and the anterior iliac crest. For each site, the personal trainer should take three measurements and then work out the average to get a more accurate result. These averages are then added together and cross-referenced on the grid to calculate an overall body fat percentage.

This method is more accurate than bioelectrical impedance, although it does rely on the practitioner’s experience and expertise. Fitness instructors should be aware of the importance of accuracy in these tests to motivate their client. For example, dehydration and failing to take measurements in the same spot each time could affect the results, and the client could become demotivated if they are led to believe they have made no progress in reducing their body fat over weeks of training.

When considering whether to administer a body fat analysis test, a personal trainer should also consider the intrusive nature of the tests. For example, for a clearly overweight client, it might be better to use the BMI index or hip-to-waist ratio, which would be easier to monitor and less intrusive.