How Calorie Deficit and Weight Loss Are Calculated
Weight loss occurs when you consistently consume fewer calories than you burn. The widely cited figure is that one kilogram of body fat contains approximately 7,700 calories. By creating a daily calorie deficit, you deplete stored fat over time. This calculation helps you estimate how long it will take to reach your goal weight at a given daily deficit.
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Formula
Calorie Deficit Calculator
Find out how long it will take to lose weight at your daily calorie deficit.
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Worked Example
Given:
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FAQs
Is a 500 calorie deficit per day safe?
A 500 kcal/day deficit is the standard recommendation for safe, sustainable weight loss of approximately 0.5 kg per week. Deficits over 1,000 kcal/day risk muscle loss, nutrient deficiency, and metabolic adaptation. Always ensure you are consuming at least 1,200 kcal/day (women) or 1,500 kcal/day (men).
Why does weight loss slow down over time?
As you lose weight, your BMR decreases because your body requires less energy to maintain a smaller mass. This is why the same deficit produces less weight loss over time. Recalculating your calorie needs every few kilograms helps keep your deficit accurate.
Does the 7,700 kcal per kg rule always apply?
The 7,700 kcal/kg figure is a useful average but varies based on the ratio of fat to muscle lost. Water retention, hormonal changes, and metabolic adaptation also affect the scale, meaning real-world weight loss is rarely perfectly linear. The calculation is a guideline for planning, not a guarantee.