How to read change between measurements

WeightWT

• Swings of a few hundred grams up to a kilogram between days are ordinary and mostly reflect digestive contents and retained water, not fat or muscle.
• If weight has fallen, look at which of the four components fell. A loss made mostly of water looks identical on the scale to a loss of fat, but means something quite different.
• Stable weight does not mean nothing is happening. Muscle mass rising while fat mass falls may not show on the scale at all.

Total body waterTBW

• Body water responds fast. The difference between morning and evening, before and after training, or before and after a meal can be noticeable without anything having changed in body composition.
• When body water rises together with muscle mass and the intracellular part rises faster than the extracellular one, that is the expected direction during strength training.
• When body water rises but mainly through the extracellular part, and the ECW/TBW ratio rises with it, that is a different situation. Always look at the ratio, not just at the sum.

ECW RatioECW/TBW

• The ratio is among the values that respond most to measurement conditions. Compare only measurements taken the same way: ideally morning, fasted, after using the toilet, without training or sauna beforehand, and after a few minutes standing.
• A difference of 0.001 to 0.003 between two measurements sits within ordinary variation. The information is in the direction across several measurements, not in a single jump.
• When the ratio jumps once, start with the measurement conditions and with what preceded them — training, a salty meal, alcohol, prolonged sitting, phase of the cycle.

Percent body fatPBF

• Compare measurements taken under comparable conditions: similar time of day, similar fluid intake, and no training or sauna immediately beforehand.
• A difference of a few tenths of a percent between two visits is not a reliable signal. What carries meaning is the trend across several measurements weeks apart.
• When the percentage falls, check that fat mass in kilograms fell too and that muscle mass held or grew. A percentage that drops while muscle disappears is a very different situation from one that drops with muscle intact.

Muscle massSMM

• Muscle mass changes slowly. A meaningful horizon for tracking is several months, not weeks — and certainly not days.
• Short-term swings come mainly from hydration, because muscle is the main water reservoir and the estimate is derived from water.
• During weight reduction the key question is whether muscle mass holds steady. Weight falling with muscle preserved is a different situation from both falling.

Visceral fatVFA

• Visceral fat usually responds to changes in diet and activity sooner than total fat mass, but even so the horizon is months, not days.
• Compare measurements under comparable conditions: fasted, at the same time of day, without training or sauna immediately beforehand. The estimate builds on body composition, so measurement conditions affect it exactly as they do the other values.
• A difference of a few cm² between two measurements is not a reliable signal. Follow the direction across three or more measurements.

Basal metabolic rateBMR

• In this calculation BMR moves only when fat free mass moves. A difference of tens of kilocalories between two measurements reflects variation in the FFM estimate, typically via hydration.
• A rise in BMR after months of strength training makes sense. A jump between two measurements days apart does not.
• The manual notes that during weight loss the body lowers its actual basal metabolic rate to conserve energy. An equation based on fat free mass cannot capture that adaptation directly — it shows only indirectly, if fat free mass falls too.

Phase angleWBPA

• The trend is the main — and, given the absent reference range, practically the only — usable information here.
• Always compare the same frequency (50 kHz for the whole body) and measurements taken under comparable conditions: similar time of day, no training or sauna immediately beforehand, similar fluid intake.
• Take seriously only a repeated shift in the same direction across several measurements. A difference between two visits can easily arise from differing measurement conditions alone.