(Bioelectrical Impedance Analysis)

BIA or Bioelectrical sensors mostly found in modern day smartwatches and wearable devices helps in detecting and measuring key body metrics beyond standard fitness tracking. Here’s how it works and whether it’s worth relying on:

What Does the BIA Sensor Measure?

• Body fat percentage
• Muscle mass
• Water percentage
• Bone mass
• Protein percentage
• Basal Metabolic Rate (BMR)

Unlike basic smartwatches that only track steps and heart rate, this feature provides deeper body composition insights, similar to high-end scales like Withings or Tanita.

How It Works

1. Electrical Impulses: A tiny, harmless current passes through your body via the watch’s electrodes.
2. Resistance Measurement: Fat, muscle, and water conduct electricity differently—higher resistance suggests more fat.
3. Algorithm Estimates: The watch combines BIA data with user inputs (height, weight, age) to generate metrics.

Note: For best results, measurements should be taken:

• In the morning (before eating/drinking).
• With dry skin (no sweat or lotion).
• Consistently (same time daily).

Accuracy: Lab-Grade or Just an Estimate?

✅ Pros:

• Convenient (no need for separate smart scales).
• Trend tracking (useful for fitness progress over time).
• Comparable to mid-range smart scales (within ~2-3% error margin).

❌ Limitations:

• Less precise than DEXA scans or medical-grade devices.
• Affected by hydration levels (dehydration can inflate fat readings).
• Wrist-based BIA is less accurate than foot/hand scales (due to lower current penetration).

Note: Useful for general trends, but not for medical or competition-level precision.