Losing 1kg per week sits at the upper safe limit for most adults but risks muscle loss and metabolic slowdown if sustained without supervision. Health authorities like CDC and NHS recommend 0.5-1kg (1-2lbs) weekly as optimal for sustainability and health preservation.
Why 1kg/Week Is Borderline Unsafe Long-Term
Rapid loss (>1kg/week) often includes:
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Muscle catabolism: 25% of loss is lean mass, dropping BMR 50-100 cal/day.
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Gallstones: 10-25% risk from fat mobilization.
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Nutrient gaps: Crash diets cause deficiencies.
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Regain: 80-95% regain within 5 years due to adaptations.
Safer alternative: 0.5kg/week prioritizes fat loss (500 cal daily deficit via diet + exercise).
Recommended Rate: 0.5-1kg/Week
Guidelines:
| Source | Rate | Rationale |
|---|---|---|
| CDC/NHS | 0.5-1kg | Sustainable, muscle-sparing |
| Mayo Clinic | 0.5-0.9kg | Long-term adherence |
| BBC Good Food | ~0.5kg | Hormonal stability |
Personalize:
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Higher BMI (>30): 1kg OK initially.
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Women/smaller frames: 0.5kg max.
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Your profile (gym, IF): 0.75kg ideal—track DEXA/body comp.
Implementation:
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Deficit: 500 cal/day (track MyFitnessPal).
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Protein: 1.6g/kg preserves muscle.
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Strength train 3x/week.
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Monitor: Weekly weigh-ins + measurements.
Bloodwork every 3 months ensures safety.
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