Key Takeaway: A sustainable caloric deficit is between 15% and 25% below your Total Daily Energy Expenditure (TDEE). This yields approximately 0.5 to 1.0 lb (0.2 to 0.5 kg) of fat loss per week while sparing muscle mass and metabolic rate.

What is a Caloric Deficit?

At its fundamental thermodynamic core, a caloric deficit occurs when the number of calories you consume through food and beverages is less than the number of calories your body expends to sustain basal metabolic function, physical movement, and nutrient digestion.

When in an energy deficit, your body is forced to oxidize endogenous fuel substrates—primarily triglycerides stored within adipose tissue—to meet its baseline ATP requirements. You can calculate your baseline expenditure using our TDEE Calculator.

Step 1: Determine Your Total Daily Energy Expenditure (TDEE)

Your TDEE is composed of four distinct metabolic components:

Basal Metabolic Rate (BMR): ~60–70% of daily burn. Calculate with our BMR Calculator.
Non-Exercise Activity Thermogenesis (NEAT): ~15% of daily burn (fidgeting, daily steps, housework).
Thermic Effect of Food (TEF): ~10% of daily burn (digestion cost).
Exercise Activity Thermogenesis (EAT): ~5–10% of daily burn (structured workouts).

Step 2: Choose Your Deficit Percentage (Avoid Crash Dieting)

Deficit Size	Daily Reduction	Projected Fat Loss	Best For
Mild Deficit (10–15%)	250–350 kcal	0.5 lb / week	Athletes, lean individuals, body recomposition
Moderate Deficit (20–25%)	400–600 kcal	1.0–1.5 lbs / week	Most individuals seeking steady, healthy fat loss
Aggressive Deficit (30%+)	750+ kcal	2.0+ lbs / week	Short-term clinical interventions (high muscle loss risk)

Step 3: Protect Muscle with Adequate Dietary Protein

When calories drop, the risk of muscle catabolism rises. Meta-analyses in the British Journal of Sports Medicine indicate that eating 1.6 to 2.2 grams of protein per kilogram of body weight (0.7–1.0g per pound) provides maximal protection against lean tissue loss during an active cut.

Use our Macro Split Calculator to establish your daily protein, carbohydrate, and fat breakdown.