Calories to lose half a kilo a week
Take your maintenance calories and subtract 550 a day. Half a kilogram of body tissue is about 3,850 kcal, and spread over seven days that is 550. For the example on this page — a 30-year-old woman, 165 cm, 65 kg, training three to five times a week — maintenance is 2,124 calories and the target is 1,574. That deficit sits inside the 500 to 1,000 kcal a day range the NHLBI clinical guidance describes for a loss of one to two pounds a week.
Your figure at each activity level
| Sedentary | 1.2 | 1,644 |
| Lightly active | 1.375 | 1,884 |
| Moderately active | 1.55 | 2,124 |
| Very active | 1.725 | 2,364 |
| Extremely active | 1.9 | 2,603 |
An estimate, not medical advice. Body metrics are population averages and do not account for your individual circumstances. Speak to a clinician about anything that matters.
The same body at every rung of the ladder. Sedentary to extremely active is about 960 calories a day apart.
The deficit is a flat 550 calories whatever your size, so as a share of maintenance it is far harsher on a small person than a large one.
Loss slows as you get lighter, because maintenance falls with weight. A target set today is out by a meaningful amount within a few kilograms.
The 7,700 kcal per kilogram rule holds for a few weeks. Hall's 2011 model puts the long-run loss at roughly half what that rule predicts.
How it works
The formula
Mifflin-St Jeor (1990), resting metabolic rate in kcal per day:
men BMR = 10 x weight + 6.25 x height - 5 x age + 5
women BMR = 10 x weight + 6.25 x height - 5 x age - 161
where
weight = kilograms
height = centimetres
age = years
Total daily energy expenditure:
TDEE = BMR x activity multiplier
1.200 sedentary
1.375 lightly active
1.550 moderately active
1.725 very active
1.900 extremely active
Calorie target for a chosen rate of weight change:
target = TDEE + (kg per week x 7700 / 7)
floored at 1200 kcal (women) and 1500 kcal (men)
What it assumes
- The equation predicts a group average rather than you. Frankenfield's systematic review found it the most reliable of the equations tested, estimating resting rate to within 10% of a measured value more often than any other, while noting that errors and limitations remain.
- The activity multiplier is a self-assessment and it is the largest source of error here. Each rung of the ladder is 0.175 of your resting rate away from the next, which is about 240 calories a day for the worked example below.
- Body composition is ignored. The equation takes total body weight, so it tends to underestimate a muscular person and overestimate somebody carrying more fat at the same weight.
- Weight change is converted at 7,700 kcal per kilogram. That holds for a few weeks and then overstates the loss, because maintenance falls as you get lighter.
- The calorie target is never displayed below 1,200 kcal for women or 1,500 for men. Those are the top of the range the NHLBI's 1998 clinical guidance prescribes for a low-calorie diet, used here as a floor.
- Nothing here accounts for pregnancy, breastfeeding, a thyroid condition, or medication that changes metabolic rate. It is not intended for anyone under 18.
- Calorie means kilocalorie throughout, which is what a food label in Britain prints as kcal and an American one prints as Calories.
Common questions
Where does the 3,500 calories per pound figure come from?
From a 1958 estimate of the energy stored in a pound of body fat, and it is a rule of thumb rather than a law. It holds reasonably for the first few months and then overpredicts, because a smaller body burns less and the deficit shrinks on its own — which is why loss slows even when the diet does not change.
Is a bigger deficit faster?
Only up to a point, and it costs more than it gains. Deficits beyond about a quarter of maintenance lose a larger share as muscle, are harder to keep to, and quietly reduce daily movement. Half a kilo a week is the usual recommendation because it is the fastest rate most people actually sustain.
Sources
- A new predictive equation for resting energy expenditure in healthy individuals
- Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review
- Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: Treatment Guidelines
- Quantification of the effect of energy imbalance on bodyweight
- Human energy requirements. Report of a Joint FAO/WHO/UNU Expert Consultation
The full method, worked example and every assumption behind this figure are on TDEE Calculator.