Measuring Body Composition: Do Scans Work Best?

Body Composition Scan

Personal training clients can prepare clean meals, hydrate sufficiently, and train properly, yet still find that truly positive results elude them. What other resources may prove useful? What might trainers suggest? Learn how a body composition scan can serve as a helpful adjunct to both weight loss endeavors and personal training.

You might explain to them that they could have lost fat, but gained muscle – accounting for the lack of change.  As they look at you with doubt, this is the moment of truth. Did you take other measurements before they started working with you? Let’s explore

Typical Methods Used to Measure Fat Loss

1. Photos.  Make sure the client wears the same outfit each time you take them and mark how far away you stand from the client so it doesn’t come out like a cheesy before and after pic. Take front and side photos. Ideally, you take the after photos when you know they lost fat.

2. Clothes. Ask the client to pick a pair of “skinny jeans” or a favorite suit that doesn’t fit anymore to make comparisons. This isn’t for everyone and can be discouraging if no changes happen.

3. Circumference. Measure their waist, belly button, hips, arms, thighs, and other areas of interest with a tape measure.

4. Bio-electrical impedance devices. Some are built into scales and others are hand-held. They aren’t very accurate on the actual percentage of fat but are good to compare pre- and post-numbers for a client who wants results but doesn’t care about norms. (See section below for an analysis of advanced body composition scans.)

5. Hydrostatic weighing. Getting dunked underwater repeatedly and paying big bucks for it isn’t for everyone. But, it’s the most accurate body fat test.

6. Skinfold Calipers. A simple device is used to pinch a fold of skin to measure a reasonable reliable amount of fat that corresponds with a body fat percentage on a reference chart.

Method Number Six Is a Winner


Set yourself apart from other personal trainers by using skinfold calipers to measure body fat. If your gym doesn’t have a pair, pitch the idea to the manager or consider buying them yourself. It’s an investment that can have big returns when people feel assured they’re getting results from their hard work. Skinfold calipers separate fat from muscle and have about 95% accuracy.

Skinfold calipers force you and the client to find out if the hard work is really paying off. Measuring body fat accurately can be eye-opening. Many people have an unrealistic view of fat. Oftentimes, people think they need to lose more than they actually do. On the flip side, some people don’t realize how high their body fat is until it’s tested.  

General Ranges for Body Fat Percentage
(Jackson, A.S. & Pollock, M.L, 1985)

Women: 10-13%
Men: 2-5%

Women: 14-20%
Men: 6-13%

Women: 21-24%
Men: 14-17%

Women: 25-31%
Men: 18-24%

Women: 32% and higher
Men: 25% and higher

Measure Body Fat with Skinfold Calipers

3-site skin fold test
Men: Chest, Abdominal, Thigh
Women: Tricep, Supra-ilium, Thigh

7-site skin fold test for both genders
Chest, Tricep, Mid-axillary, Sub-scapula, Abdominal, Supra-ilium, Thigh

9-site (Parillo 9-site formula) test for both genders
Chest, Bicep, Tricep, Sub-scapular, Mid-axillary, Abs, Supra-iliac, Thigh, Calf

Ensuring Accuracy with Body Composition Testing

Hydrostatic weighing is the gold standard for body fat testing. Getting close to that accuracy requires the personal trainer to know where the skin fold sites are and how to measure properly. Practice is essential for perfecting this skill.

Follow These Guidelines to Avoid Common Mistakes

1. Pinch the skin and fat in line with the underlying muscle. The tricep, abdominal, and thigh are vertical; chest and suprailium are diagonal and the mid-axillary and sub-scapula are horizontal.

2. Have the person flex their muscle for two seconds to ensure you aren’t pinching it along with the fat and skin.  Make sure they relax before you record the measurement.  

3. Place the calipers in the middle of the pinch. It’s a common mistake to place the calipers too close to where the skin is being pulled and get a larger number than what’s accurate.

4. Hold the pinch for a few seconds to let the calipers sink into the skin. Be gentle when taking them off. Open the calipers completely so as not to scratch the client.

5. Measure each site twice and a third time if the first two numbers are more than 2mm different. Add the measurements together and divide by the number of times measured.

Tricep: 2,5,5  becomes 2 + 5 + 5 = 12.  Divide 12 by 3 = 4mm.

6. When you have the average number for each site (tricep, suprailium, thigh, etc.), add them up. Use a chart or calculator online to calculate the body fat percentage.  You’ll need the client’s age and gender.  Some calculators online ask for their height, weight and, activity level also.  This is usually to calculate Body Mass Index (BMI).

Tricep 4, Supra ilium 10, and Thigh 15, become 4 + 10 + 15 = 29mm total.
Don’t divide this number by three!  This is the sum or total of the sites measured.

7. Mark the results with the date and re-measure every 3-4 weeks.  Use the same side of the body each time you repeat the test.

Skinfold testing tells the client what area they are holding the most fat and how much fat they have compared to muscle on their body. If they lose fat and gain muscle, the skin fold test will show this.  Then your client will believe you when you say, “You lost fat and gained muscle.”


First measurement: 24% fat and weighs 130 lbs. = 31.2 lbs. fat, 98.8 lbs. muscle

Four weeks later: 20% fat, still weighs 130 lbs. = 26 lbs. fat, 104 lbs. muscle

No weight was lost according to the scale….

Yet…how many pounds of FAT did this sample client lose?  5 lbs.

The scale WON’T show this change.

Advanced Skinfold Caliper Testing

If you already use skinfold calipers and want to take your knowledge to the next level, BioSignature is a skinfold caliper method that pairs body fat with hormone malfunction. Charles Poliquin developed this 12-site skinfold testing method. This test adds knee, calf, quadriceps, hamstrings, chin, and cheek to the other seven sites above.  The results help the practitioner to make nutritional recommendations. Special training is required to administer this body composition test.

One Last Tip
Consider buying a fat and muscle replica to show clients who are looking to lose weight.  Many people are tactile and will understand their bodies better when you show them the difference between a pound of fat and muscle.

Body Scans, Stats, and Predictions

Body composition scans, a new and innovative assessment that requires very little of a client’s time, aim to measure the bone, fat, and muscle makeup of one’s body. Such an analytical rendering can benefit both the client and his trainer when embarking upon a new workout program. A clearer understanding of one’s body helps to identify problem areas, making goal-setting even easier.

Trainers often counsel clients not to obsess about a number on the bathroom scale, since lean muscle mass does in fact weigh more than adipose (fat) tissue, and can often account for weight gains at the start of exercise programs. This concept, while often a tough sell, is corroborated in a body scan.

There are a few different technologies out there with slightly different approaches to measuring body composition. Popular brands have both in-home and gym models of varying degrees of complexity and offerings. This body scan works by sending harmless electrical impulses throughout the body, known as bioelectrical impedance analysis (DSM-BIA).

While not directly measuring body fat, such scans make use of formulas to surmise the body composition of fat, muscle, water, etc. based on the conductivity of the water it detects; different tissue will vary in the amount of electricity it can conduct based on the content of water it contains.

Some budget models of these scanners only send impulses through the hands like this Omron, and others, just the feet. Higher-end models of total body comp scanners like InBody will also send impulses through both the hands and feet, which looks like a large stand-on scale with handles.

Accounting for human nature when making even educated guesses, we must expect a certain deviation of standard in terms of error, and not assume 100% accurate predictions.

The Imaging Process

Further, other commercial scanners provide a 360-degree imaging scan of the entire body, such as the Shape Scale. While this does not utilize bioelectrical impedance to estimate fat/lean mass, it gives you an actual photographic representation of fat versus muscle, so that body composition progress can be tracked over time.

In fitness and health centers that offer this type of body composition scanning to their clientele, the client stands on a platform with arms outstretched and hands clenched into loose fists. The platform then begins its 360-degree rotation, accomplished in under a minute. Through the use of a harmless infrared light that reflects off the body, the machine comes up with digital measurements similar to those taken with a tape measure.

The difference between this analysis and manual measurements that trainers take involves greatly reducing the aspect of human error. This 3-dimensional model of a client’s body helps in quantifying surface area and volume; all of these values combine to predict a very close approximation of an individual’s body composition.

While such an analysis must still take into account some small degree of error, the efficacy of these body composition scans piqued the interest of the National Institutes of Health. The NIH subsequently approved a tremendous amount of funding to two separate body composition companies, to expand the industry’s scope of knowledge on body scanning research. Clearly this leading icon feels strongly about the scanners’ potential for commercial use and eventual availability at more fitness centers and nutritionists’ offices.

Learn more in our Functional Training Specialist as a part of our Continuing Education Course Series.
Functional Training Specialist course

Many Factors Influence Body Composition Scan Results

During a workout, bodily fluids get concentrated in the area upon which the exercises focus, by way of providing nutrients and removing waste products. Following a workout, core body temperature increases, thereby lowering electrical impedance and decreasing the apparent percentage of body fat. Conversely, a cooler body temperature elicits an increase in electrical impedance, which reflects a lower amount of fat-free mass.

Total body water (TBW), estimated through electrical impedance, can help to calculate fat-free mass. Scientists base these calculations on the assumption that water comprises 73-77% of the body’s fat-free mass, with bone, muscle, organs, etc, remaining. A key conceptual problem lies in the frequently misunderstood fact that fat-free mass (or lean mass) and lean muscle mass are not interchangeable terms, an error commonly made even by fitness professionals. Lean mass/fat-free mass is anything that is not adipose tissue, and lean muscle mass is only the percentage of that lean mass that is muscle. Clients must understand that an increase in fat-free mass does not necessarily mean they have put on more lean muscle tissue.

 “Success” is Best Assessed by the Client’s Perception

Many professionals feel that body composition scans may not accurately reflect either body composition or a client’s progress. The most important way of assessing progress should take into consideration how the client “feels” in his own skin. After that, trainers might consider the use of photos and circumference measurements to assess periodic progress. The client can best judge how his clothing fits, while also honestly looking at improvements in his fitness abilities, strength, energy, sleep patterns, and meal planning.

Finally, ask the clients directly, “How do you feel about yourself and your past efforts as you move towards your goal?” This idea, beyond all other measuring tools, helps to empower the client, providing him with a sense of mastery over his process towards an ultimate goal, and the maintenance beyond.


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Cathleen Kronemer is an NFPT CEC writer and a member of the NFPT Certification Council Board. Cathleen is an AFAA-Certified Group Exercise Instructor, NSCA-Certified Personal Trainer, ACE-Certified Health Coach, former competitive bodybuilder and freelance writer. She is employed at the Jewish Community Center in St. Louis, MO. Cathleen has been involved in the fitness industry for over three decades. Feel free to contact her at [email protected]. She welcomes your feedback and your comments!