Bioimpedance is sensitive to the water in your body, so the conditions you test under matter as much as the device. Test at the same time, in the same state, every time, and you can trust the trend.
Why conditions matter
BIA estimates body composition from how easily a small current passes through your body, and water is what carries it. Anything that shifts your water balance (food, fluids, exercise, alcohol, heat, menstrual cycle) can move the reading even though your fat and muscle have not changed. Clinical guidelines on BIA stress standardized measurement conditions for exactly this reason.
The 7-step protocol
- Same time, same day. Pick one or two mornings a week and keep them.
- Empty bladder. Use the bathroom first.
- Before food and big drinks. Test before breakfast and before your morning coffee or a large glass of water.
- No exercise beforehand. Test before your workout, not after; sweat and blood flow change readings.
- Skip alcohol the night before test days when you can.
- Clean, dry contact. Bare feet and hands on the electrodes, no lotion, stand still in the same position.
- Same device, same settings. Keep your profile (height, age, sex, activity level) up to date and never compare across different devices.
How to read your results
- Track a rolling 2–4 week average, not a single day.
- Focus on lean mass and body fat direction more than the exact number.
- Confirm the trend with a DEXA scan every 8–12 weeks.
For clinics: standardize the visit
If you offer in-clinic BIA, put the same rules on your booking confirmation: morning appointments, no workout beforehand, bathroom before the scan. A consistent protocol is what makes month-over-month comparisons meaningful for your clients. The DEXA+ CORE program includes ready-made scan protocols and intake forms for this.
Frequently asked questions
Why did my body fat jump overnight?
Most overnight swings are water: a salty meal, alcohol, a hard workout or dehydration all change resistance. Look at the 2–4 week trend instead.
What time of day is best for a BIA reading?
Morning, after using the bathroom and before eating, drinking a lot or exercising, is the easiest time to repeat consistently.
Should I use BIA during my period?
Fluid shifts during the menstrual cycle can change readings. Note the cycle day, or compare readings from the same phase of each cycle.