Coming back to: An 18-month record including the parts that went badly

Picking up post #2: that is the part I would want checked first.

Menstrual cycle: for people who menstruate, weight can shift by several pounds across the cycle due to fluid retention and other factors. Noting cycle phase when weighing reduces apparent noise.

Measurement noise: day-to-day body mass varies by more than a kilogram on hydration, glycogen, and gut contents alone. A weekly reading is a single noisy sample of a distribution. A seven-day rolling mean of daily readings has much lower noise.

Worth separating two things that post #24 runs together.

Medication changes: escalating dose, or adding or removing other medications, can affect the rate of weight loss. Documenting medication changes alongside weight makes the record interpretable.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

Rate of change: reporting progress as "lost 5 kg in 12 weeks" is more useful than "currently at 82 kg" because the rate tells you whether the change is steady, accelerating, or stalling.

This follows post #49 rather than contradicting it.

Seasonal patterns: some people report weight loss is slower in winter than summer. Body composition and activity changes might contribute. Noting the season is useful context.

Menstrual cycle: for people who menstruate, weight can shift by several pounds across the cycle due to fluid retention and other factors. Noting cycle phase when weighing reduces apparent noise.

Protein intake and resistance training: both self-reported and therefore optimistic in most reports. Recording them anyway creates a record you can look back on.