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How big should your calorie deficit be?

Paul Hummel Last reviewed June 10, 2026 3 min read
How big should your calorie deficit be?
Quick answer

A moderate calorie deficit of 300 to 500 kcal per day is frequently cited as a workable range. It corresponds to losing roughly 0.5 to 1 percent of your body weight per week.

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Estimate based on 1 kg of body fat ≈ 7,700 kcal (Hall et al., 2011).

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Sustainable rate: 0.5–1% of body weight per week (Helms et al., 2014). Aggressive deficits promote muscle loss.

The moderate range

A deficit of 300 to 500 kcal below total daily energy expenditure translates to a fat loss of roughly 0.3 to 0.5 kg (0.7–1.1 lb) per week. Helms et al. (2014) discuss this range in their review as a practical approach for dieting phases.

Chart: moderate calorie deficit of 300 to 500 kcal per day

Steeper deficits come with downsides

In a controlled study, Garthe et al. (2011) compared a moderate deficit (0.7 percent weight loss per week) with an aggressive one (1.4 percent). Individual studies have shown more favorable outcomes with moderate deficits than with aggressive ones.

PaceRecommendation
Slow (0.5%/week)300 kcal deficit
Moderate (0.7%/week)400–500 kcal
Aggressive (1%/week)500–700 kcal (short-term only)
At higher body fat levels, the body tolerates larger deficits. The leaner you are, the more important a moderate approach becomes to avoid losing muscle (Helms et al., 2014).

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GymLog AI calculates your individual target deficit and warns you when you drift too far off course.

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Sources

  1. Helms, E. R., et al. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. JISSN, 11:20. jissn.biomedcentral.com
  2. Garthe, I., et al. (2011). Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. Int J Sport Nutr Exerc Metab, 21(2). PubMed
This content is for general informational purposes only and is not a substitute for medical, nutritional, or therapeutic advice. If you have a medical condition, are pregnant, or take medication, please consult a qualified professional. Recommendations apply to healthy adults.