How the weight change calculator works
The 3,500 rule and its fine print
A pound of body fat stores roughly 3,500 kcal, so a 500 kcal daily deficit loses about a pound a week — a useful first-order model. The fine print: the rule holds best over months, not days (water, glycogen, and adaptation mask it weekly), TDEE falls as weight falls, and metabolism adapts to aggressive deficits. The calculator applies the rule with a rate limit for exactly those reasons.
Why 1% per week is the ceiling
Faster loss pulls protein from muscle along with fat, tanks training quality and adherence, and triggers the rebound that erases the effort. One percent of body weight weekly (0.5–1 lb for most, more for heavier individuals) preserves muscle, keeps hunger manageable, and produces the before-and-after photos that actually last.
The recalculation loop
TDEE is a moving target: lighter bodies burn less, adapted bodies burn less, and plateaus are arithmetic, not failure. Recalculate maintenance every 10 lb (or whenever two weeks of honest tracking shows no trend) — the plan is a living number, not a signed contract.