The Basic Maths of Fat Loss
One kilogram of body fat contains approximately 7,700 kcal. To lose 1kg per week, you'd need a daily deficit of 1,100 kcal, which for most people is too aggressive to sustain without muscle loss and metabolic adaptation.
A 500 kcal/day deficit produces roughly 0.5kg of fat loss per week, the recommended sustainable rate. This means losing 10kg takes approximately 20 weeks, or around 5 months.
| Goal | At 0.25 kg/wk | At 0.5 kg/wk | At 1 kg/wk |
|---|---|---|---|
| 5 kg | 20 weeks | 10 weeks | 5 weeks |
| 10 kg | 40 weeks | 20 weeks | 10 weeks |
| 15 kg | 60 weeks | 30 weeks | 15 weeks |
| 20 kg | 80 weeks | 40 weeks | 20 weeks |
Why The Scale Lies
Body weight fluctuates by 0.5-2kg on a daily basis due to water retention, food volume, hormonal changes and glycogen levels. This daily noise makes it impossible to judge progress day-to-day. Use weekly averages, weigh daily under the same conditions and average the week's readings.
The first 1-2 weeks of a diet often show a rapid drop (2-3kg) from water and glycogen loss, this isn't fat loss. Equally, the scale may not move for a week or two despite real fat loss occurring, masked by water retention.
What Affects The Timeline
Several factors influence how quickly you'll reach your goal: starting body fat (higher body fat = faster initial loss), deficit size, how consistently you stick to your targets, and whether you're resistance training (which preserves muscle and keeps metabolic rate higher).
Progress also slows as you lose weight, your TDEE decreases as you get lighter, so the same food intake produces a smaller deficit over time. Recalculate your TDEE every 4-6 weeks to keep targets accurate.
