What Is a Calorie Deficit?
A calorie deficit occurs when you consume fewer calories than your body burns. Your body turns to stored fat to make up the difference. One pound of fat stores approximately 3,500 calories. To lose 1 lb per week, you need a deficit of 500 calories per day.
How to Calculate Your TDEE
TDEE (Total Daily Energy Expenditure) is total calories burned daily including activity.
Step 1 — BMR (Mifflin-St Jeor for women):
BMR = (10 × weight kg) + (6.25 × height cm) – (5 × age) – 161
Example: 35-year-old, 68kg, 163cm: BMR = 680 + 1018.75 – 175 – 161 = 1,363 calories
Step 2 — Multiply by activity:
- Sedentary: × 1.2
- Lightly active (1–3 days/week): × 1.375
- Moderately active (3–5 days/week): × 1.55
- Very active (6–7 days/week): × 1.725
Example, lightly active: 1,363 × 1.375 = 1,874 calories TDEE
How Large Should Your Deficit Be?
Aggressive (750–1,000 cal/day below TDEE): 1.5–2 lbs/week. Risks muscle loss, metabolic adaptation, and diet fatigue. Not recommended for more than 4–6 weeks.
Moderate (500 cal/day below TDEE): ~1 lb/week. The gold standard. Fast enough to see progress, slow enough to preserve muscle and metabolism.
Small (250 cal/day below TDEE): 0.5 lbs/week. Ideal for preserving athletic performance during weight loss.
Metabolic Adaptation
When you eat less, your body adapts by burning fewer calories. This is why weight loss slows after 6–8 weeks. To counteract it: use a moderate deficit, keep protein high, and include strength training.
Practically Speaking
For the woman in our example (TDEE 1,874): a 500-calorie deficit means eating 1,374 calories daily. For most women 5'2"–5'6", this lands in the 1,300–1,500 calorie range — enough to eat real, satisfying meals with planning.
