Body Fat Analysis

A personal trainer will sometimes use a body fat analysis test on a client as a good indicator of 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 to use a Dual-energy X-ray Absorptiometry or DEXA machine, which analyses both bone density and body fat percentage. However, because they are expensive to buy, 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 calipers. 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 specifically targets the upper body, it’s useful for 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 disadvantages of these methods is that there can be some discrepancies in the measurements. For example, as water does not conduct electricity particularly well, if the personal trainer’s client is dehydrated it can give a lower reading than when they are fully hydrated. Human and computer error can also be factors.

Skin calipers

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

The four-point skin caliper test

The four-point skin caliper test focuses on the upper body, which is the danger area 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 take into account the intrusive nature of the tests. For example, for a client who is clearly overweight, it might be better to use the BMI index or hip-to-waist ratio, which would be easier to monitor and less intrusive.