How big should my calorie deficit be?

A deficit of 500–750 kcal per day (about 0.5–0.75 kg per week) is considered safe and sustainable for most people. Larger deficits increase the risk of muscle loss, fatigue, and metabolic slowdown. Start moderate and adjust based on your progress and energy levels.

Can I build muscle in a calorie deficit?

Yes, especially if you are a beginner, returning after a break, or carry significant body fat. This is called body recomposition. It requires high protein intake (1.6–2.2 g/kg), progressive resistance training, and adequate sleep. The leaner you are, the harder it becomes.

How fast should I lose weight?

Most experts recommend 0.5–1% of body weight per week. For an 80 kg person, that is 0.4–0.8 kg per week. Losing faster than this increases the risk of muscle loss and is harder to sustain. Patience and consistency beat aggressive dieting every time.

What macros should I eat in a deficit?

A good starting point is 40% protein, 30% carbohydrates, and 30% fat. Protein is the priority — it preserves muscle, keeps you full, and has the highest thermic effect. Adjust carbs and fat based on your preferences and training demands.

Why has my weight loss stalled?

Plateaus are normal. Common causes include metabolic adaptation, water retention (especially after increasing exercise or sodium intake), underestimating portions, and unconscious calorie creep. Try a 1-week diet break at maintenance, then resume your deficit.

Should I eat back exercise calories?

Generally, no — or at most, eat back 50% of estimated exercise calories. Fitness trackers and machines overestimate calorie burn by 30–50%. Your TDEE already accounts for your general activity level. Eating back all exercise calories often erases the deficit entirely.

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Calorie Deficit Calculator

Find out exactly how many calories you need to eat to lose weight at your chosen pace — safely and sustainably.

How the Calorie Deficit Is Calculated

We use the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR), then multiply by your activity level to get your Total Daily Energy Expenditure (TDEE):

Target = TDEE − (goal kg/week × 1,100 kcal)

Calculate your BMR

The Mifflin-St Jeor equation uses your weight, height, age, and gender to estimate how many calories your body burns at complete rest. Men: 10×weight(kg) + 6.25×height(cm) − 5×age + 5. Women: same formula − 161.

Estimate your TDEE

Your BMR is multiplied by an activity factor (1.2 for sedentary up to 1.9 for extremely active) to estimate your total daily calorie burn, including exercise and daily movement.

Apply the deficit

To lose 1 kg of body fat, you need a cumulative deficit of roughly 7,700 kcal. We divide your weekly target by 7 to get a daily deficit — for example, losing 0.5 kg/week requires a 550 kcal/day deficit.

Why a Calorie Deficit Is the Only Way to Lose Fat

No matter what diet you follow — keto, intermittent fasting, paleo, or anything else — fat loss only happens when you consistently eat fewer calories than your body burns. This is the law of energy balance, and it applies universally.

Energy balance is physics — if you consume fewer calories than you burn, your body taps into stored fat for the difference
Every diet that works does so by creating a calorie deficit, whether or not it explicitly tracks calories
The best deficit is one you can sustain — aggressive cuts lead to muscle loss, metabolic slowdown, and eventual rebound
Your metabolism adapts to prolonged dieting — periodic diet breaks and refeeds can help maintain metabolic rate
Strength training during a deficit is critical — it signals your body to preserve muscle and burn fat preferentially
Higher protein intake (1.6–2.2 g/kg) during a deficit protects lean mass and increases satiety

Tips for a Successful Calorie Deficit

1Eat enough protein — aim for 1.6–2.2 g per kg of body weight to preserve muscle and stay full longer
2Keep lifting weights — resistance training is the strongest signal to preserve muscle mass during a deficit
3Start with a moderate deficit — losing 0.5 kg/week is sustainable and minimizes muscle loss
4Track your intake for at least 2 weeks — most people underestimate calories by 30–50% without tracking
5Prioritize 7–9 hours of sleep — sleep deprivation increases hunger hormones and reduces willpower
6Increase daily steps to 8,000–10,000 — walking burns calories without increasing appetite
7Be patient with plateaus — weight loss is not linear, and water retention can mask fat loss for weeks
8Schedule diet breaks — 1–2 weeks at maintenance every 8–12 weeks helps prevent metabolic adaptation

Common Calorie Deficit Myths Debunked

"Eating too little puts you in starvation mode"

Metabolic adaptation is real but modest — your metabolism may slow by 10–15% during prolonged dieting, not shut down entirely. True starvation mode only occurs in extreme cases of malnutrition. A reasonable deficit (500–750 kcal/day) will not stop fat loss.

"Eating less is always better for weight loss"

Excessively low calories cause muscle loss, hormonal disruption, nutrient deficiencies, and binge eating. A moderate deficit preserves muscle, keeps energy stable, and is far more sustainable long-term. More restriction does not mean faster results.

"All calories are equal for body composition"

While energy balance determines weight change, macronutrient composition affects body composition. 2,000 calories of protein-rich whole foods will preserve more muscle and burn more energy through digestion than 2,000 calories of processed carbs and fat.

"You must do cardio to lose weight"

Cardio burns calories but is not required for fat loss — your diet creates the deficit. In fact, excessive cardio without strength training can accelerate muscle loss. Walking and resistance training are far more effective for body composition than hours on the treadmill.

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Frequently Asked Questions

How big should my calorie deficit be?: A deficit of 500–750 kcal per day (about 0.5–0.75 kg per week) is considered safe and sustainable for most people. Larger deficits increase the risk of muscle loss, fatigue, and metabolic slowdown. Start moderate and adjust based on your progress and energy levels.
Can I build muscle in a calorie deficit?: Yes, especially if you are a beginner, returning after a break, or carry significant body fat. This is called body recomposition. It requires high protein intake (1.6–2.2 g/kg), progressive resistance training, and adequate sleep. The leaner you are, the harder it becomes.
How fast should I lose weight?: Most experts recommend 0.5–1% of body weight per week. For an 80 kg person, that is 0.4–0.8 kg per week. Losing faster than this increases the risk of muscle loss and is harder to sustain. Patience and consistency beat aggressive dieting every time.
What macros should I eat in a deficit?: A good starting point is 40% protein, 30% carbohydrates, and 30% fat. Protein is the priority — it preserves muscle, keeps you full, and has the highest thermic effect. Adjust carbs and fat based on your preferences and training demands.
Why has my weight loss stalled?: Plateaus are normal. Common causes include metabolic adaptation, water retention (especially after increasing exercise or sodium intake), underestimating portions, and unconscious calorie creep. Try a 1-week diet break at maintenance, then resume your deficit.
Should I eat back exercise calories?: Generally, no — or at most, eat back 50% of estimated exercise calories. Fitness trackers and machines overestimate calorie burn by 30–50%. Your TDEE already accounts for your general activity level. Eating back all exercise calories often erases the deficit entirely.