FAT TESTING IS A SCAM

FAT TESTING IS A SCAM SUMMARY 

• Fat testing on many digital devices can lead to erroneous results.

• Dehydration can lead to overestimating body fat percentage, and overhydration can lead to underestimating percent body fat.

• Bodyfat analysis is highly variable among individuals; body fat % errors ranged from +11.1% to -6.5% in 95% of subjects

ARE DIGITAL BODYFAT CALIPERS ACCURATE?

A female friend recently asked me to go with her to a major gym franchise because the gym sales counselor told her that she needed to buy one-on-one personal training. After she got her body fat tested and she was classified as obese.

She was not overweight and exercised casually, around three days a week.  The female  joined a new gym as part of her new year’s resolution to lose weight, as many women do.  After she was classified as obese, she really became depressed.

I just sat back and casually observed the conversation. The gym sales counselor showed me the digital fat caliper (aka fat meter) she was evaluated on, which was the Omron Monitor. The Omron is a handheld device in which you stand up, place your hands on the two silver handles, and wait 5 seconds, and your % body fat (BF) is analyzed.

These devices fall under what is called bioelectrical impedance (BIA). The device runs a small electrical current through the body. The counselor measured her body fat after her workout; this is important, as you will read below.

FAT TESTING IS A SCAM: BIA

The premise of BIA testing is that muscle is mostly water, and fat has little water. By determining the resistance of the signal as it passes thru your body, you can predict someone’s % BF and lean muscle. Despite BIA’s convenience, water intake can significantly impact the test results.

Dehydration can lead to overestimating body fat percentage, and overhydration can lead to underestimating percent body fat. (O’Brien et al., 2002)

Her % body fat was found to be 32% which was right on the high side, and she was considered obese. The sales counselor showed me her BMI and body measurements for weight loss chart. The average % body fat for women was 25-31%, so she was right on edge.  Dehydration leads to an overestimation of body fat, so whether the counselor intentionally did this to make her body fat higher than she really was could have been a sales tactic to get a personal trainer.

IS PERSONAL TRAINING WORTH IT?

The counselor recommended having a personal trainer train her on a routine for three days a week. I asked, “how much does personal training cost?” The personal trainer cost for three days a week, with each resistance training session lasting 30 minutes, was $495 a month.

Most personal trainers’ hourly rates can range from 40-150$ per hour, depending on the trainer. So, expect to pay for their services.

Working with a personal trainer offer many benefits for health and fitness. Personal trainers hold you accountable for exercise sessions, educate on proper form, and motivate you to train harder. Personal training sessions are a valuable way for people looking for professional supervision while training and offering expertise in exercise mastery.

FAT TESTING IS A SCAM

The counselor asked my friend, “what is your ideal body fat?” My friend wanted to get in fitness shape and told the counselor that her ideal body fat was 21-24%. The counselor then clicked on the image of a woman with 21-24% body fat and told her that in 3 months, she could easily lose 10% of her body fat. Note: The average % body fat loss in resistance-trained studies without diet is 1.4%.(Wewege et al., 2022)

The counselor laid out the program for her to meet with a trainer three days a week. The program would be 30 minutes of aerobic exercise and 30 minutes of resistance training. The counselor kept emphasizing that you need to burn calories to lose fat.

There was no nutritional counseling with a registered dietician in this program. So based on this program, there was no help with the diet; just burn the fat off with exercise. As discussed previously, exercise without diet is a bad solution for fat loss.

Let’s break down the issues with this program.

BF TESTING

Using body composition machines for fat analysis, such as the Omron and digital body fat calipers, are notoriously inaccurate. In 2016, two studies examined the accuracy of handheld body composition machines (i.e., commonly used in gyms) and skinfold calipers which a person pinch the fat and measure how much body fat a person has. These were then compared to the gold standard for measuring muscle and fat, which is a DEXA machine. A DEXA machine costs about $150-300 for a test.

The study analyzed 130 people (67 men and 63 women). The average error for the handheld device was 0-4%. The individual level of inaccuracy was much worse. On an individual level, body fat % errors ranged from +11.1% to -6.5% in 95% of subjects. (Nickerson et al., 2017)

This means that if your body fat % is 32%, like my friend, her real body fat can be as low as 20.9% or as high as 43.1%. In another study, 20 out of 50 people had 8 pounds less body fat than they really had using BIA. (Ritz et al., 2007)

Another study used the exact same Omron BIA body fat in the gym used in many gyms and compared it to other body fat procedures. The Omron BIA error range was 21.9% compared to skinfold testing, which was 11.7%

When measuring %BF in bodybuilders, BIA ranked one of the worse methods for accuracy (~8% error rate) compared to DEXA and other methods. (van Marken Lichtenbelt et al., 2004) The moral of the story is that %bf reading is garbage and can’t be used with any degree of accuracy.

SMART SCALES ARE JUST AS BAD

Smart scales that hook up to your phone have been advocated to measure body fat. A recent study examined three of the leading smart scales in people: normal weight, overweight, and obese.

All the scales were accurate for weight but not for body composition. All underestimated fat mass compared to DEXA. Scale 1 was off by -2.2 kg (-4.8 lbs.), Scale 2 was off by -4.4 (-9.7 lbs.), and scale 3 was off by – 3.7 kg (8.7 lbs.).

In terms of muscle mass, 1 scale underestimated muscle mass, while the other two overestimated muscle mass. (Frija-Masson et al., 2021)

BEST WAY TO TRACK BODYFAT

A more accurate way is taking regular tape measurements around the arms, waist, legs, etc. Also, use the mirror to gauge how your fat loss is progressing, excluding the % BF reading. Skinfolds by a well-trained technician are a better estimate of true % body fat losses.

If you have access to an underwater weighing machine, that is also acceptable. If you want to use a bodyfat scale or some other testing device, just realize that these devices have a high degree of error and are probably not even worth using.

Ultimately, she decided to train on her strength training on her own without working with a trainer. Anyone walking into a gym is cautious if the counselor wants to make you pay for a personal trainer after a body composition assessment test. These tests have a high degree of inaccuracy, and my friend could very well have a normal body fat %, but the testing device registered her as obese.

REFERENCES

Frija-Masson, J., Mullaert, J., Vidal-Petiot, E., Pons-Kerjean, N., Flamant, M., & d’Ortho, M.-P. (2021). Accuracy of Smart Scales on Weight and Body Composition: Observational Study. JMIR mHealth and uHealth, 9(4), e22487-e22487. https://doi.org/10.2196/22487

Nickerson, B. S., Esco, M. R., Bishop, P. A., Schumacker, R. E., Richardson, M. T., Fedewa, M. V., Wingo, J. E., & Welborn, B. A. (2017). Validity of Selected Bioimpedance Equations for Estimating Body Composition in Men and Women: A Four-Compartment Model Comparison. J Strength Cond Res, 31(7), 1963-1972. https://doi.org/10.1519/jsc.0000000000001648

O’Brien, C., Young, A. J., & Sawka, M. N. (2002). Bioelectrical impedance to estimate changes in hydration status. Int J Sports Med, 23(5), 361-366. https://doi.org/10.1055/s-2002-33145

Ritz, P., Sallé, A., Audran, M., & Rohmer, V. (2007). Comparison of different methods to assess body composition of weight loss in obese and diabetic patients. Diabetes Res Clin Pract, 77(3), 405-411. https://doi.org/10.1016/j.diabres.2007.01.007

van Marken Lichtenbelt, W. D., Hartgens, F., Vollaard, N. B., Ebbing, S., & Kuipers, H. (2004). Body composition changes in bodybuilders: a method comparison. Med Sci Sports Exerc, 36(3), 490-497. https://doi.org/10.1249/01.mss.0000117159.70295.73

Wewege, M. A., Desai, I., Honey, C., Coorie, B., Jones, M. D., Clifford, B. K., Leake, H. B., & Hagstrom, A. D. (2022). The Effect of Resistance Training in Healthy Adults on Body Fat Percentage, Fat Mass and Visceral Fat: A Systematic Review and Meta-Analysis. Sports Medicine, 52(2), 287-300. https://doi.org/10.1007/s40279-021-01562-2