Body weight has become an obsession with many individuals. I am no different. As with all biological measurements, body weight may vary within and between days depending upon such biological factors such as diet, hydration, activity among other factors. Of course, there may be also technical errors such as type of equipment (analog vs digital), device calibration, device reliability among others.
Body weight was measured on a Withing’s Body Smart digital scale twice daily, once in am after awakening and a walk into bathroom and secondly in the evening just prior to bedtime. This was done from August 2023 until October 2024 for a total of 169 paired days (including both AM and PM); many days were consecutive and many days were conveniently done. Only underwear shorts were worn for each measurement.
Additionally, other weights were recorded at convenient times randomly during other days over this time period. Analog weights were recorded by hand dating from 1985 until 2022 without regard to time of day or day of week.
Below are the weight distributions from 1984 until 2024 without regard to time of day or scale type.
Next is a graph of mean weight (and 95% CI) over the years.
Distributions of weight by scale type (Analog, Digital) and time of day (AM, Mid, PM). Note that analog scale alone was used prior to 2023 and then digital scale alone.
Distributions of weight for the 169 paired AM and PM days.
Paired t-test of weight AM and PM. Body weight is 2.11 lbs higher in the PM than in the AM.
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut elit tellus, luctus nec ullamcorper mattis, pulvinar dapibus leo.
The next analyses shows the previous night’s valvue paired against the next AM value. Note the difference is that these data are on different days with the shortest time between (only sleep time). The differences are similar to the within day differences; 2.12 lbs higher weight in the PM vs the next AM (SE of differences = 0.060 lbs).