What Is a Sustainable Calorie Deficit (Without Losing Muscle)

A calorie deficit always works in theory. In practice, 80% of diets fail because people choose deficits that are too aggressive and lose muscle, health, and motivation.

How Much Deficit Is 'Too Much'

Helms et al. 2014 establish safe ranges: 0.5-1% of body weight per week. For 80 kg, that is 400-800 g/week, equivalent to a daily deficit of 440-880 kcal.

Why Faster Is Worse

• Greater lean mass loss (up to 35% of weight lost is muscle on aggressive deficits).
• Sharp drop in leptin and testosterone.
• Accelerated metabolic adaptation: your TDEE drops faster than your weight.
• Very low adherence: 70% quit in less than 12 weeks.

How to Preserve Muscle in a Deficit

1. Raise protein to 2.0-2.4 g/kg.
2. Keep strength training with heavy loads (maintenance, not progression).
3. Limit excessive cardio: 2-3 quality sessions beat 6 mediocre ones.
4. Sleep 7-9 h: recovery during a deficit is critical.
5. Consider 1-2 week 'diet breaks' at maintenance every 8-12 weeks of cutting.