Basal Metabolic Rate
Calories your body burns at complete rest — the foundation of energy expenditure.
Plain English
Patient-Friendly Explanation
Your BMR is the number of calories your body burns just to stay alive — breathing, thinking, pumping blood. It accounts for 60-75% of your daily calorie burn.
Medical
Clinical Definition
BMR is measured under strict conditions (12h fasted, thermoneutral environment). Predictive equations (Mifflin-St Jeor) estimate BMR from weight, height, age, and sex. Lean body mass is the main determinant.
Key Insight
Why It Matters
BMR decreases with weight loss (metabolic adaptation), making continued weight loss harder. Medical supervision helps adjust strategies as metabolism changes.
What BMR is
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — keeping your heart beating, lungs breathing, brain working and cells maintaining themselves. For most people it is 60–75% of daily energy use: the biggest line in your energy budget.
What determines your BMR
The main drivers, in order:
- Muscle mass — muscle is metabolically expensive; every kilogram raises resting burn
- Body size — bigger bodies burn more at rest
- Age — resting metabolism declines roughly 1–2% per decade after 30, mostly because muscle is lost
- Thyroid status and genetics — smaller but real influences
- Sex — men typically have higher BMR per kilogram because they carry more muscle
BMR vs TDEE
BMR is only part of the picture. Total Daily Energy Expenditure (TDEE) adds everything else:
- BMR: calories at complete rest (~60–75% of daily use)
- Thermic effect of food: calories burned digesting meals (~10%)
- Activity: walking, exercise, fidgeting and daily movement (the rest)
- TDEE = BMR + digestion + activity. Your calorie target is set against TDEE, not BMR
- BMR estimates from formulas (e.g., Mifflin-St Jeor) are close but never exact — the clinic uses them as a starting point, adjusted by results
Why BMR falls during dieting — and what to do
This is the 'metabolism slow-down' people talk about — and it is real but manageable:
- Losing weight lowers BMR partly because you are smaller (less body to run) and partly through metabolic adaptation — the body defends its set point
- Crash dieting causes the steepest drop, because muscle is lost alongside fat
- Resistance training preserves muscle, which defends BMR
- Adequate protein (1.2–1.6 g/kg) and a modest deficit keep the fall proportionate to the weight lost
- Re-feeding weeks (temporarily eating at maintenance) can blunt adaptation during long cuts
Common questions
What is Basal Metabolic Rate?
The calories your body burns at complete rest — the energy cost of staying alive. For most people it is 60–75% of total daily energy use and is the largest component of your calorie budget.
How do I calculate my BMR?
Formulas like Mifflin-St Jeor estimate it from age, sex, height and weight (e.g., men: 10×kg + 6.25×cm − 5×age + 5). Estimates are a starting point only — the clinic adjusts them against your actual results and body composition.
Why did my metabolism slow down on my diet?
Two reasons: you're smaller (less body to maintain) and your body adapts to the deficit by burning slightly less (metabolic adaptation). The fall is steeper on crash diets because muscle is lost. Resistance training and adequate protein minimise it.
Can I increase my BMR?
Yes — the reliable lever is muscle. Gaining or preserving muscle raises resting burn, which is why resistance training and protein are core parts of the clinic's weight-management plans. Thyroid and genetics matter, but they are not something most people can change.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: August 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
