Tool / wearable
Smart Scales (BIA Body Composition)
Last updated Sat May 30 2026 00:00:00 GMT+0000 (Coordinated Universal Time)
How BIA works
Bioelectrical impedance analysis passes a small electrical current through the body and measures resistance. Different tissues conduct differently; algorithms estimate fat and lean mass from impedance plus height, weight, sex, age.
Why absolute values shouldn’t be trusted
- Hydration status dramatically affects readings (more water = appears more lean).
- Recent meal, exercise, alcohol, menstrual cycle all shift readings.
- Foot-to-foot scales only measure lower-body impedance; upper-body composition is estimated by inference.
- Algorithms differ between manufacturers — absolute values can disagree by 5–10 percentage points body fat.
Why trends are still useful
- If you measure under consistent conditions (same time of day, hydrated similarly, post-bathroom, pre-breakfast), the trend over weeks to months is informative.
- Useful for detecting unintended weight gain/loss patterns.
When DEXA is better
For absolute body-composition values, DEXA scan is the reference. For trend tracking at low cost, BIA is reasonable.
Practical tips
- Same scale, same time of day, similar hydration.
- Track 7-day moving averages, not daily values.
- Pair with waist circumference (better for visceral-fat trend than BIA-estimated visceral fat).