A DEXA scan gives you the most accurate snapshot of fat, muscle and bone, but most people only scan every 8 to 12 weeks. Bioimpedance (BIA) fills the gap: weekly readings show whether you are trending in the right direction, so you can adjust before your next scan.
Why DEXA alone leaves a gap
A DEXA scan measures fat mass, lean mass and bone density directly, region by region. That precision is why clinics and researchers call it the gold standard for body composition. The trade-off is frequency: you book an appointment, travel to a clinic and usually repeat it every 8 to 12 weeks.
A lot happens in 12 weeks. If your nutrition, training or medication is pushing you toward muscle loss instead of fat loss, you want to know in week three, not week twelve. That is where bioimpedance comes in.
What bioimpedance measures
Bioelectrical impedance analysis (BIA) sends a very small, painless electrical current through the body and measures how much it resists that current. Lean tissue holds a lot of water and conducts electricity well; fat conducts poorly. Software turns that resistance into estimates of body fat percentage, lean mass, visceral fat and body water.
Eight-electrode (segmental) devices, like the DEXA+ Body Fat Scale, read through both hands and both feet, which captures more of the body than foot-only bathroom scales.
DEXA vs. BIA: use each for what it does best
| DEXA scan | Bioimpedance (BIA) | |
|---|---|---|
| Best for | Accurate baseline and checkpoint numbers | Frequent trend tracking |
| How often | Every 8–12 weeks | 1–2 times per week |
| Measures | Fat, lean and bone mass directly, by region | Estimates fat, lean mass and water from resistance |
| Affected by hydration | Minimally | Yes, so test under the same conditions |
| Where | Clinic | Home or clinic |
A simple tracking routine
- Get a DEXA baseline. Book a scan before you start a new program, diet or medication.
- Take a BIA reading the same week. This becomes your starting point for trends on the scale.
- Measure once or twice a week at the same time of day, after using the bathroom, before eating or exercising.
- Watch the 2–4 week trend, not single readings. A one-day jump in body fat is usually water, not fat.
- Re-scan with DEXA every 8–12 weeks to confirm what the trend suggested and recalibrate your expectations.
What to do with the trend
- Weight down, lean mass steady, body fat down: you are losing mostly fat. Keep going.
- Weight down, lean mass falling: you may be losing muscle. Talk to your coach or provider about protein intake and strength training before your next DEXA.
- Weight flat, body fat down, lean mass up: classic body recomposition. The scale weight hides real progress.
Start with an accurate baseline, then track the trend at home.
Find a DEXA scanShop the DEXA+ Body Fat ScaleFrequently asked questions
How often should I use a bioimpedance scale between DEXA scans?
Once or twice a week, under the same conditions each time, is enough to see a trend. Daily readings add noise from hydration and food.
Will my BIA body fat number match my DEXA result?
Usually not exactly. BIA estimates body composition from electrical resistance, and different devices read higher or lower than DEXA. Use BIA for direction of change and DEXA for the accurate number.
How often should I get a DEXA scan?
Every 8 to 12 weeks while you are actively changing your body composition, at the same location each time.