Journal · Evenly · Scales and data
Body fat on a home scale: what it can and can’t tell you
A plain guide to bioimpedance, the reasons your reading moves, and better ways to see change.
Goldmend Health4 min read · 7 November 2026
Your scale says your body fat is 28 percent. Yesterday it said 27. Did you gain fat overnight? Almost certainly not.
How the scale guesses
Most home scales use bioelectrical impedance analysis, or BIA. Metal pads under your feet send a very small, safe current through your body. Lean tissue holds more water and lets the current pass more easily than fat. The scale measures how much the current is resisted, then a formula combines that with your height, age and sex to estimate body fat.
Notice the word estimate. The scale does not see fat. It infers it.
Why the number moves
- Hydration. Drinking a lot, sweating, or a salty meal changes the reading.
- Feet. Dry or cold feet, socks, or standing off-centre change contact with the pads.
- Timing. Readings after exercise or a meal differ from morning readings.
- The formula. Different brands use different formulas, so two scales can disagree by several points.
Who should be careful
Manufacturers advise against using body-fat mode if you have a pacemaker or other implanted electronic device, and many advise against it in pregnancy. Check your scale’s manual. Evenly lets you turn body-fat readings off and save weight only.
Better ways to see change
- Waist measurement every two to four weeks.
- How clothes fit. A belt notch is a real result.
- Strength. If your lifts go up while your weight is steady, you are probably building muscle.
- Progress photos, taken in the same light, kept private.
What Evenly shows
Evenly shows body fat as "about 28% (estimate)" and focuses on its direction over weeks. If you link a strength-training app, Evenly can show "weight steady, strength up", a pattern that often means you are adding muscle.
This article is general information, not medical advice.
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