A calorie target calculated at your starting weight becomes a smaller deficit as you lose weight, because a lighter body burns less. For a 35-year-old woman of 170 cm doing light exercise, maintenance falls from 2,030 calories a day at 75 kg to 1,893 at 65 kg — so a target of 1,480 that began as a 550-calorie deficit is a 412-calorie deficit ten kilograms later.
That is the plateau, and most of it is arithmetic rather than metabolism. The rest is the part people find harder to accept.
What does the deficit actually do over time?
A kilogram of body fat holds roughly 7,700 calories, so a 550-calorie daily deficit is about half a kilogram a week. Hold the target fixed and the weekly loss falls as the maintenance figure comes down to meet it.
| Weight | Maintenance | Fixed target | Actual deficit | Weekly loss |
|---|---|---|---|---|
| 75 kg | 2,030 kcal | 1,480 kcal | 550 kcal | 0.50 kg |
| 70 kg | 1,961 kcal | 1,480 kcal | 481 kcal | 0.44 kg |
| 65 kg | 1,893 kcal | 1,480 kcal | 413 kcal | 0.38 kg |
The rate has dropped by a quarter without anything changing except body weight. Someone tracking carefully sees the scale slow and concludes the plan has stopped working, when the plan is doing exactly what its arithmetic said it would.
Where does the fall in maintenance come from?
Two thirds of it is the basal rate. The Mifflin–St Jeor equation puts basal metabolic rate at 1,476.5 calories for that person at 75 kg and 1,376.5 at 65 kg — 100 calories lower simply because there is less body to run. The activity multiplier then scales that difference up to the 137-calorie fall in the maintenance figure.
There is also less work to do. Moving a lighter body costs less, so the same walk, the same stairs and the same training session all burn slightly less than they did.
The effect compounds with the goal. Someone aiming to lose 15 kg will see the maintenance figure fall by roughly 200 calories across the attempt, so a target set once at the start spends the second half of the journey running a deficit about 40 per cent smaller than the one that produced the early results.
What is adaptive thermogenesis?
The additional slowdown beyond what body size alone predicts. Prolonged energy restriction reduces expenditure by more than the equations expect — through lower non-exercise movement, small hormonal changes and reduced spontaneous activity — and this is on top of the arithmetic above.
The size of the effect is debated and it is real. It also means the equation, which knows only your height, weight, age and sex, systematically overestimates maintenance for someone several months into a deficit. The practical reading: if the scale has been flat for a fortnight and the food logging is honest, maintenance is probably below what the calculator says.
What are the actual options when it slows?
Four, and only one of them is cutting further.
- Recalculate. Enter the current weight rather than the starting one. This alone restores the deficit you intended.
- Check the activity band. It is the biggest single source of error in the estimate, and people rarely revise it downward when training drops off.
- Audit the logging. Underreporting intake creeps up over months, and it does so without anyone deciding to do it.
- Cut further. The last resort rather than the first, because the floor is real: below about 1,500 calories a day it becomes difficult to meet protein and micronutrient needs, and that range warrants medical supervision.
Why does the same plan work differently for two people?
Because the equation is a population average and individual resting metabolism varies by roughly 10 per cent either way at identical size. Two people of the same height, weight, age and sex can genuinely differ by 150 calories a day before anyone has moved.
Add the variance in the activity multiplier and the honest accuracy of any calculated target is a range rather than a number. The number is a starting hypothesis; the scale over four weeks is the measurement.
How often should the target be recalculated?
Every four or five kilograms, which for most people is every six to ten weeks. Recalculating more often chases noise; less often lets the deficit erode far enough that progress stalls and the plan looks broken.
Recalculating is also the moment to revisit the activity band, because training volume drifts over months in both directions. A band that was honest in January is a guess by April.
Questions people ask
Should I eat back exercise calories? If the activity multiplier already reflects your training, doing so double-counts it. Bands are the more common approach precisely because they fold exercise into the estimate once.
Is a bigger deficit faster? Faster and less durable. Large deficits increase the share of the loss that comes from lean tissue and make adherence harder, and the resulting lower body mass lowers maintenance further.
Why does my weight jump overnight? Water, glycogen and gut contents, which move by a kilogram or more day to day. A weekly average is the only reading with any signal in it.
Does the 7,700 figure hold exactly? It is a reasonable estimate for fat tissue and not a constant. Early losses include water and later ones include some lean tissue, so the conversion is approximate at both ends.
Recalculate at the current weight before concluding anything has broken. The calorie calculator sets the target, the TDEE calculator shows what each activity band is worth, and the BMI calculator puts the healthy weight range next to where you are now.