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In a calorie deficit but not losing weight

If you are genuinely eating less than you burn, you are losing fat. The energy has nowhere else to go. So when the scale will not move, one of two things is true: the deficit is smaller than you think, or fat loss is happening and something is hiding it.

Here are the causes in roughly the order they are likely.

1. The deficit is smaller than you think

This is the most common answer by a wide margin, and the hardest to accept, because it does not feel like it applies to you.

It is rarely dishonesty. It is the oil the vegetables were cooked in, the “handful” of nuts that was 60 g, the bites while cooking, the milk in four coffees, the portion estimated generously because weighing felt excessive. Each is small. Together they routinely close a 500 kcal gap.

Test it: weigh everything, with no estimating at all, for seven days. Not forever — just long enough to find out whether your usual estimates are accurate. Most people discover a few hundred calories they did not know about. Reading a label properly closes most of the rest, since the dry-versus-cooked distinction alone can double a figure.

One particular version of this deserves naming, because it looks like diligence: eating back your exercise calories. A watch reports the gross burn for a session, including the energy you would have spent sitting still. Eat all of it back and you have credited yourself for the baseline twice — a 400 kcal run might be only 330 kcal of genuinely extra burn. If you eat exercise calories back at all, eat back about half, and read how accurate the figure is first.

2. You are judging it over days, not weeks

Fat loss at a 500 kcal deficit is about 1 lb a week. Daily weight swings of 2–4 lb are completely ordinary — food volume in transit, salt, carbohydrate and its associated water, hormones, sleep, bowel timing.

The signal is smaller than the noise. Over a single week it can be entirely invisible.

Test it: weigh daily, same conditions, and compare weekly averages over at least four weeks. Three weeks of a flat scale is not evidence of anything; three weeks of flat weekly averages, with weighed food, is.

3. Water is masking it

Fat loss and weight loss are not the same thing, and water moves faster than either.

New or harder training causes muscles to retain water while they repair. A salty meal holds water for days. Stress and poor sleep raise cortisol, which does the same. For anyone who menstruates, cycle-related retention can hide two weeks of fat loss and then disappear overnight — which is why the scale sometimes drops 3 lb in a morning you did nothing special.

Fat loss continued the whole time. The scale was reporting water.

4. Five good days, two bad ones

A 500 kcal deficit across five weekdays banks 2,500 kcal. Two relaxed days at 1,250 over maintenance erase it exactly.

This pattern is extremely common and nearly invisible from the inside, because the weekdays feel disciplined and the weekend feels like “just a bit off plan”.

Test it: track a full seven days — including both weekend days — and look at the weekly total rather than the daily one. Building the week around protein and volume helps here — see what a calorie deficit diet actually is.

5. Your maintenance is lower than the calculator said

Every maintenance figure starts as an estimate. Mifflin–St Jeor carries about ±10%, and the activity multiplier is blunt: the gap between “lightly active” and “moderately active” is nearly 300 kcal.

If you have also been dieting a while, your maintenance has fallen — partly because you are lighter, partly through metabolic adaptation, and partly because incidental movement drops during a deficit without you choosing it.

Test it: recalculate from your current weight, then subtract 100–150 kcal and hold it for three weeks. How to calculate a deficit walks through it.

6. Something medical

Occasionally there is a genuine cause: thyroid dysfunction, PCOS, certain medications including steroids and some antidepressants.

This is last on the list because it is genuinely uncommon relative to the first five — but if you have carefully ruled those out over two months of weighed food and weekly averages, it is worth a conversation with a doctor rather than another cut.

What to do this week

  1. Weigh food properly for seven days, weekend included.
  2. Weigh yourself daily; compare weekly averages, never single days.
  3. Give it four weeks before concluding anything.
  4. Only then adjust intake — by 100–150 kcal, not 500.

The reason this is hard is that a deficit is invisible while it is working. Caldown exists for that: it accumulates the deficit as a single falling number so a flat week on the scale does not look like a flat week of effort — one of several trackers that do not charge monthly.

More on running a calorie deficit and how big yours should be.

General information, not medical advice.