What Is a Calorie Deficit?
A calorie deficit is a state in which you consume fewer calories per day than you burn. This is the most fundamental, scientifically proven principle of weight loss.
When energy runs short, your body breaks down stored body fat and uses it for fuel. Accumulating a deficit of about 7,700kcal results in the loss of 1kg of body fat.
The Right Deficit Size
Cutting calories too aggressively can cause muscle loss, nutrient deficiencies, and a slower metabolism. Here are healthy deficit targets.
| Level | Deficit per day | Loss per week |
|---|---|---|
| Beginners | 300–500kcal | 0.3–0.5kg |
| Intermediate | 500–750kcal | 0.5–0.7kg |
| Maximum recommended (short term only) | 1,000kcal | 1kg |
Eating less than 1,200kcal per day (women) or 1,500kcal per day (men) is not recommended without medical supervision.
Calculating Your BMR
Basal Metabolic Rate is the minimum energy your body needs to stay alive even when doing nothing. You can calculate it with the Harris-Benedict formula.
- •Men: BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) - (5.677 × age)
- •Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) - (4.330 × age)
For example, a 30-year-old man (80kg, 175cm) has a BMR of about 1,820kcal. Multiply by an activity factor to get your Total Daily Energy Expenditure (TDEE).
Applying an Activity Factor
TDEE (Total Daily Energy Expenditure) = BMR × activity factor
| Activity level | Factor |
|---|---|
| Little to no exercise | BMR × 1.2 |
| Light exercise (1-3 times/week) | BMR × 1.375 |
| Moderate exercise (3-5 times/week) | BMR × 1.55 |
| Active (6-7 times/week) | BMR × 1.725 |
| Very active | BMR × 1.9 |
Practical Deficit Tips
- •Log your food: check calories with the app before you eat
- •Protein first: keeps you full and prevents muscle loss
- •Drink enough water: 2L+ per day, 500ml before meals
- •Cut processed foods: they hide a lot of calories
- •Weigh in once a week: daily weigh-ins just add stress
“Dieting is a marathon, not a sprint. Lose it fast and it comes back fast.”
Sources · Korea Ministry of Food and Drug Safety food composition database