Weight Loss Calculator

Doubling the rate halves the timeline and doubles the hunger. The 2 lb/week row sits at the edge of what most guidelines allow, and for many people it means eating below 1,500 kcal a day — the floor where micronutrient intake and lean mass start to suffer.

The 0.5 lb/week row is the opposite trap: a 250 kcal deficit is easy to erase by accident. One underestimated restaurant meal, or a weekend that runs 800 kcal over, turns a 60-week plan into a flat line.

Three effects push the date out, and none of them appear in the formula.

Energy expenditure falls as you lose weight. A lighter body burns less at rest and costs less to move, so the 1,900 kcal that produced a 500 kcal deficit at 200 lb may produce a 300 kcal deficit at 175 lb. That alone stretches the last third of any plan.

Adaptive thermogenesis cuts deeper than mass alone predicts. Non-exercise activity — fidgeting, walking, standing — drops by roughly 100-300 kcal/day in a sustained deficit. You do not decide to move less; the body spends less on the same movement.

Water and glycogen. Sodium, carbohydrate intake, and the menstrual cycle move the scale 2-4 lb in either direction within a week. One flat week is not a plateau. Three or four flat weeks with a verified intake is.

The practical fix is unglamorous: recalculate every 5-10 lb, and judge progress on a seven-day average instead of a single morning.

The usual ceiling is about 1% of body weight per week — 2 lb for a 200 lb person, 1.2 lb for someone at 120 lb. That scaling is exactly why a flat 2 lb/week target is wrong for smaller bodies, and why a 120 lb person following a generic 1,200-calorie plan often loses lean mass along with fat.

The other limit is intake. 1,200 kcal/day for women and 1,500 for men is the common minimum without medical supervision, because below it, hitting protein, iron, calcium, and B12 needs becomes a puzzle rather than a diet.

Slower is not automatically better either. A 250 kcal deficit requires accurate tracking to exist at all; a plan that is 100 kcal off in either direction is not a slow plan, it is maintenance with extra steps.

The rule comes from Max Wishnofsky's 1958 paper: a pound of adipose tissue stores roughly 3,500 kcal, so a 500 kcal/day deficit should remove a pound a week. The arithmetic is right; the assumption underneath it is not. It treats the body as a fixed-cost engine, when expenditure falls as mass falls — and it ignores that early loss includes glycogen and its bound water, often 3-5 lb in the first two weeks.

That is why week one looks like a triumph and week three looks broken. Nothing changed in your behaviour; the water left and the fat loss continued at its real, slower rate.

Dynamic models (the NIH body-weight planner uses Hall's) produce a slower, curved trajectory. For goals under about 30 lb the straight-line answer is close enough to plan with. For larger goals it is optimistic by 20-30%.

Weigh at the same time, ideally after waking and before eating, and average the last seven days. Compare weekly averages, never daily readings — daily weight swings more than weekly fat loss.

If the seven-day average has not moved in three weeks and intake is genuinely tracked, change one thing: cut about 100-150 kcal, or add 1,500-2,000 steps a day. Do not do both at once, or you will not know which one worked.

Resistance training matters for a second reason. In a deficit, some of the loss is muscle, and muscle is what keeps TDEE from falling as fast. Two sessions a week plus roughly 1.6 g of protein per kg of body weight preserves most of it.