What is a calorie deficit?
A calorie deficit occurs when you consume fewer calories than your body uses. Faced with this energy shortfall, your body turns to its stored energy — primarily fat — to make up the difference. Sustain that deficit over time and you lose weight. It's the underlying mechanism behind every successful diet.
The 3,500-calorie rule
A pound of body fat stores roughly 3,500 calories (a kilogram, about 7,700). So a daily deficit of 500 calories adds up to about one pound of fat loss per week. This is a useful rule of thumb, though real-world results vary with water, muscle, and metabolic adaptation.
How to calculate your deficit
- Find your maintenance calories with the TDEE calculator.
- Subtract 300–500 calories for a moderate, sustainable deficit.
- That number is your daily intake target.
The weight loss calculator turns this into an estimated timeline to your goal weight.
How to create the deficit
You can build a deficit two ways — eat less or move more — and the best approach combines both:
- Nutrition: prioritize protein and fibre to stay full on fewer calories.
- Activity: daily steps (NEAT) burn surprising amounts of energy.
- Training: resistance work preserves muscle so the weight you lose is fat.
Avoid an aggressive deficit
It's tempting to slash calories for faster results, but very large deficits cause muscle loss, fatigue, hormonal disruption, and intense hunger that leads to bingeing. A moderate deficit you can sustain for months beats a crash diet you abandon in two weeks.
When progress stalls
As you lose weight, your maintenance calories fall, shrinking your deficit. Recalculate every 4–5 kg and adjust. Patience and consistency win.