How this is worked out, and its limits
CDC and NHS describe 0.5 to 1 kg a week as the safe, sustainable pace. A cumulative deficit of about 7700 kcal is taken as one kilogram of fat, so 500 kcal a day is about 0.5 kg a week. This is an estimate: the body adapts and the pace slows over time.
References: CDC, steps for losing weight
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