If you have ever tried to lose or gain weight deliberately, you have run into two acronyms: BMR and TDEE. They are the foundation of calorie planning, and confusing them is one of the most common reasons a diet quietly fails.
BMR: your body at idle
Basal Metabolic Rate is the energy your body uses just to stay alive — breathing, circulating blood, maintaining temperature, running your organs — if you did absolutely nothing all day. For most adults it accounts for the largest share of daily calorie use, often 60–70%.
BMR is usually estimated with the Mifflin-St Jeor equation, which uses your weight, height, age, and sex. It is an estimate: real metabolism varies with muscle mass, genetics, and hormones, but the formula is accurate enough for planning.
TDEE: BMR plus everything you do
Total Daily Energy Expenditure is your BMR multiplied by an activity factor that accounts for movement — walking, exercise, even fidgeting. It is the number that actually matters, because it is how many calories you burn on a real day.
| Activity level | Multiplier (× BMR) |
|---|---|
| Sedentary (little exercise) | 1.2 |
| Lightly active (1–3 days/week) | 1.375 |
| Moderately active (3–5 days) | 1.55 |
| Very active (6–7 days) | 1.725 |
Turning TDEE into a goal
Weight change comes down to energy balance. To lose weight, eat below your TDEE; to gain, eat above it. A pound of fat stores roughly 3,500 calories, so a daily deficit of about 500 calories tends to produce roughly a pound of loss per week — a sustainable pace for most people. Aggressive deficits backfire by costing you muscle and willpower.
Why your BMR is not fixed
- Muscle raises it. Muscle tissue burns more energy at rest than fat, so strength training nudges your BMR upward over time.
- Dieting can lower it. Sustained calorie restriction causes the body to become more efficient, which is why weight loss often slows.
- Age lowers it. BMR tends to decline gradually with age, partly due to muscle loss.
Frequently asked questions
Should I eat below my BMR to lose faster?
Generally no. Eating below BMR for long stretches is hard to sustain and can cost muscle. Create the deficit from your TDEE instead, and be patient.
How accurate are these estimates?
Formulas get most people within a reasonable margin, but individual metabolism varies. Use the number as a starting point, then adjust based on how your weight actually responds over a few weeks.
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Results are for general information only and are not professional financial, medical, or legal advice.