Don’t Use Bioelectric Impedance to Measure Body Fat

Recently, a 70-year-old client of mine wanted to add high-intensity interval training to her regimen, so she decided to join a local gym. As part of her membership, she was given a free assessment which involved a method of measuring body fat known as bioelectric impedance.

Bioelectric impedance works by sending a small electrical current through the body and depending on how much resistance is encountered, it can measure total body water which is used to estimate body fat. It’s not the most accurate way to assess body composition, but it’s common in many health clubs.

The Shocking Results

My client was expecting some decent results from the assessment – after all, she’s been eating right and training consistently for many years – but the results were not decent at all! With a straight face, the trainer told my client that she’s 44% body fat and needs to lose 16 pounds.

First of all, no trainer should ever tell a client how much weight they need to lose. To tell a 130-pound healthy individual that she needs to lose 16 pounds is ridiculous and completely unprofessional.

Furthermore, this client is in pretty good shape. To suggest that practically half her body is made up of fat is just nonsense. You don’t have to be an expert to realize that the results are inaccurate.

A similar incident occurred with bodybuilding coach John Parrillo and one of his top female athletes. Listen to this interview at around the 9:16 mark for the story.

Take-Home Message: Factors like body fluid amounts, hydration status, and electrode placement can influence the results of a bioelectric impedance analysis. Look for other methods to measure body fat, such as a DEXA scan or skinfold measurements, that are more accurate and show the distribution of fat throughout the body.

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