Calorie Deficit Guide

How to lose fat while preserving muscle mass during a cut.

6 min read
January 15, 2026
Part ofNutrition Basics Guide

Quick answer: A 500 calorie deficit per day is optimal for losing ~0.5kg/week of fat while preserving muscle. Keep protein high (2.0-2.2g/kg) and don't reduce training intensity.

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What is a Calorie Deficit?

A calorie deficit means eating fewer calories than you burn (TDEE). This forces your body to use energy reserves (fat) to make up the difference.

Formula:

Deficit = TDEE - Calories Eaten

If TDEE = 2500 and you eat 2000, deficit = 500 kcal/day

How Much Deficit is Optimal?

DeficitLoss/WeekMuscle RiskSustainability
250-300 kcal0.25-0.3kgMinimalHigh
500 kcal ⭐0.5kgLowGood
750 kcal0.7-0.8kgModerateMedium
1000+ kcal1+kgHighLow

How to Preserve Muscle in a Deficit

Do This

  • • High protein: 2.0-2.2g/kg
  • • Maintain intensity (same weights)
  • • Reduce volume if needed, not intensity
  • • Sleep 7-9 hours
  • • Moderate deficit (max 500 kcal)

Avoid This

  • • Too aggressive deficit (>750 kcal)
  • • Reducing weights in the gym
  • • Too much high-intensity cardio
  • • Low protein (<1.6g/kg)
  • • Deficit for >16 weeks straight

Cutting Duration

Recommendation: 8-16 weeks of cutting

After 16 weeks, metabolism adapts and loss slows. Do 4-8 weeks at maintenance before resuming.

Cardio in a Deficit: Yes or No?

Cardio is optional. The deficit comes from diet, not exercise. If you do cardio:

  • Prefer LISS (walking, easy cycling) - doesn't interfere with recovery
  • 10,000 steps/day is enough for most people
  • Don't use intense HIIT - it competes with weight training

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Frequently Asked Questions

What is a good calorie deficit for fat loss?

A deficit of 300-500 calories per day is optimal for fat loss while preserving muscle. This results in 0.3-0.5kg (0.7-1lb) of fat loss per week. Larger deficits (750-1000 kcal) speed up fat loss but increase muscle loss risk and are harder to sustain.

How long should I stay in a calorie deficit?

Most cutting phases last 8-16 weeks. Longer than 16 weeks increases metabolic adaptation and muscle loss risk. After a cut, transition to maintenance calories for 4-8 weeks before cutting again or starting a bulk.

Will I lose muscle in a calorie deficit?

Some muscle loss is possible, but you can minimize it by: keeping protein high (2.0-2.2g/kg), maintaining training intensity (don't drop weights), keeping deficit moderate (500 kcal max), and getting adequate sleep. Most people can cut with minimal muscle loss following these guidelines.

Should I do cardio or just diet for fat loss?

Diet creates the calorie deficit; cardio is optional but can help. A 500 calorie deficit from diet alone works perfectly. If adding cardio, use low-intensity cardio (walking) to avoid interfering with recovery. Don't rely on cardio to 'burn off' overeating.