Our body composition scales use BIA (Bioelectrical Impedance Analysis) technology, which is highly reliable and repeatable. However, the hydration levels of the body significantly affect the results.
- Lower hydration = Higher body fat reading
- Higher hydration = Lower body fat reading
This is because BIA measures impedance (resistance to electrical flow), which changes with body water levels. Fluctuations in the results are normal and do not indicate a defect in the scale.
What causes these fluctuations?
Your body weight and hydration levels can fluctuate throughout the day, and from day to day, due to several factors:
• Food & drink intake – Eating and drinking directly add weight, while certain foods (especially salty or high-carb meals) cause temporary water retention.
• Exercise – Sweating reduces body water, which can temporarily increase body fat readings. Strength training can also cause short-term water retention in muscles.
• Sleep – You lose water overnight through breathing and sweating, so hydration levels are often lower in the morning.
• Hormonal changes – Menstrual cycles, stress hormones, and other hormonal shifts influence water retention and fat distribution.
• Salt & alcohol intake – Salt can cause the body to retain extra water, while alcohol dehydrates, temporarily altering readings, also the following day.
• Stress & illness – High stress or being sick can lead to changes in hydration due to hormone fluctuations, fever, or inflammation.
• Temperature & humidity – Hot weather or high humidity can increase sweating and dehydration or cause water retention, while cold environments may reduce circulation and alter skin conductivity.
• Bathroom habits – Bathroom visits directly affect both weight and hydration levels.
Even measuring twice in a row can show differences. This is normal and expected due to natural changes and skin conductivity (e.g., warm vs. cold feet and/or hands).
How can I get consistent measurements?
For the most accurate tracking, measure under consistent conditions:
✔ Same time of day (preferably a few hours after waking)
✔ Before eating a large meal or drinking lots of fluids
✔ Before exercising
✔ After using the bathroom
✔ In the same environment & at room temperature
✔ Use the same body composition scale each time
How should I interpret my results?
A single measurement is just a snapshot of that specific moment. Change happens over time, and instead of focusing on daily changes, we recommend to look at weekly and monthly trends. We recommend averaging multiple readings over time to track real and long term change and progress.
To get the most accurate results from your TANITA, here you can find more tips to create the best measurement routine: How to get the best results from my TANITA?
For more information about how the technology works see: How does TANITA measure body composition?