Your maintenance calories aren't a permanent number. As your body changes, the target that worked at the start quietly stops working — and knowing when to recalculate is the difference between steady progress and a frustrating stall.
A lighter body burns fewer calories doing the same things, so every kilogram you lose lowers your TDEE a little. The calorie target that produced a clean deficit at your starting weight becomes a smaller deficit — and eventually maintenance — if you never update it.
You can re-run the calculator with your current weight — that captures the weight-driven part of the drift. But formulas can't see metabolic adaptation or your individual variation. The more accurate approach once you have a few weeks of data is to calibrate against what actually happened: the tracker infers your real maintenance from your weight trend, which already includes any adaptation. Use the formula early, then let your own data take over.
When you do adjust, move in modest increments — around 100–150 calories — rather than slashing intake. Big cuts accelerate the very adaptation you're trying to outrun, and they're harder to sustain.
Every 10–15 lbs of weight change, or whenever progress stalls for 2–3 consistent weeks. Age-related change is slow enough that annual is fine for that factor.
No. Daily weight swings 1–2 kg from water and food in transit. Look for 2–3 weeks of no trend before treating it as a real stall.