What a basal metabolic rate actually is
Your body burns energy lying still. Keeping the heart beating, breathing, holding body temperature — all of it costs.
That baseline is your basal metabolic rate.
It accounts for 60–70% of what you burn in a day. Exercise takes a much smaller slice, around 5–10%.
That is why losing weight on exercise alone is such hard work.
Daily needs are your BMR multiplied by how much you move
Multiply the baseline by your activity level and you get what you actually burn in a day.
Eat that much and your weight holds. Eat less and it comes down.
How much less should you eat
Losing 1 kg of body fat means running a deficit of roughly 7,700 kcal.
At 500 kcal a day, that works out to about 2 kg a month.
The temptation is to cut harder. Try not to go below your basal rate.
Muscle goes first, and once muscle goes your baseline drops too — which makes the next kilogram harder than the last.
⚠️ Worth knowing
This uses the Mifflin-St Jeor equation. It is widely used, but it is still an estimate.
Two people at the same height and weight can differ a lot depending on muscle mass.
The activity multipliers are rough too.
The most accurate approach is to log what you eat for a couple of weeks and adjust based on what the scale actually does.
If you are pregnant, breastfeeding or managing a health condition, do not use these numbers as they are. Talk to a doctor.