So what is this B.I.A. scale ?
Bioimpedance (electric) analysis also known as a BIA scale, measures body composition (fat mass, fat-free mass) by sending a small electrical current through your body. Usually in a scale form, it estimates how the current is resisted. The issue with this it relies heavily on assumptions (height, age, sex, hydration, body shape). Evidence supports this in multiple populations.
From the systematic review with Di Vincenzo et. al. (2021), in obese adults, the electrical phase angle differs in delivering accurate measures of body fat percentage, and the current validity across multiple studies is flawed.
Why? Because of the researchers found a lack of standard measuring evidence with hydration status, food intake, recent exercise, even skin temperature can influence the reading. For example, several studies with the BIA scale show differing measurement standards across multiple studies in the systematic review. An example would be the following; one day you step on the scale and your hydration is slightly off or you just worked out, and your BIA reading shifts.
Additionally, the prediction equations built into many BIA devices are derived from average populations. That means if your body doesn’t match that “average” (by age, ethnicity, body type, training status), the estimate may be off.
Why does this matter?
The magnitude of error in BIA scales may create psychological stress and frustration. If you’re being sold or asked to use a BIA to reference your body fat percent you may want to reconsider. Some studies show that difference can be several percent of body fat, which for you might mean misinterpreting whether you’re making progress or not.
👉 Bottom line: BIA can give you a number — but that number may not reflect what’s actually happening inside your body, especially if you use it as the sole metric for progress.
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✅ What to use instead (or in addition) to track progress
Since you want meaningful progress, here are tools we use that get our FITTWAVE clients coaching results that are more reliable:
1. Option 1: Scale (bodyweight) – simplest metric which you can measure daily. We at FITTWAVE recommend doing this daily and before you eat or drink anything. While it doesn’t tell you fat vs muscle directly, tracking your weight over time consistently (same time of day, same conditions (fasted in the morning)) gives you useful trend data. We discuss this on our Youtube. Watch a full breakdown here of someone who has felt stuck even with measuring bodyweight the same.
2. Option 2: Tape measure + body circumference – waist, hips, thighs, arms, chest. These measures tell you where you’re losing or building, and often change faster than the scale.
3. Option 3: Progress photos – front/side/back pictures in the same light/pose/clothing every few weeks. Visual changes are powerful especially with monitoring weight trends over time and workout performance in the gym.
4. Performance metrics – how you feel in the gym, how many reps you’re doing, how your clothes fit, how your energy is. These reflect functional results.
5. If available: body composition assessment via more accurate methods – such as Dual‑Energy X‑Ray Absorptiometry (DXA) or skin fold calipers by a qualified practitioner. Use less frequently (quarterly maybe) to benchmark.
6. Coach Austin’s recommendation. BEST OPTION Combining metrics – Use at least 2-3 of the above so you’re not relying on one number. That gives you a more complete picture.
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