BMR

BMR - Basal Metabolic Rate

Definition

BMR (Basal Metabolic Rate) represents the number of calories your body burns at complete rest to maintain its vital functions: breathing, blood circulation, temperature regulation, organ function, etc.

It is the minimum energy your body needs if you stayed lying down all day without moving. BMR makes up 60 to 75% of your daily energy expenditure.

💡 BMR is different from TDEE (Total Daily Energy Expenditure), which also includes physical activity, digestion (thermic effect of food), and NEAT.

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Why know your BMR?

BMR is the foundation of all nutrition calculations. Knowing it lets you:

• Accurately calculate your TDEE (by adding your activity)
• Set a realistic caloric deficit for cutting
• Calculate your surplus for bulking
• Understand why you gain or lose weight
• Adapt your intake to your goals

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Factors that influence BMR

BMR varies enormously between individuals. The main factors:

Factor	Impact on BMR
Muscle mass	+++ (muscle is highly energy-demanding at rest)
Sex	++ (men generally have a higher BMR)
Age	-- (BMR drops 1-2% per decade after age 20)
Height / Weight	++ (taller / heavier = higher BMR)
Genetics	+/- (natural variation between individuals)
Thyroid hormones	+/- (strongly influence metabolism)
Outside temperature	+ (cold slightly raises BMR)

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How to calculate your BMR

Several formulas exist. The 2 most accurate:

1. Mifflin-St Jeor formula (recommended)

The most accurate formula for the general population, validated by many studies.

For men:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5

For women:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161

Concrete example: 30-year-old man, 80 kg, 180 cm
BMR = (10 × 80) + (6.25 × 180) - (5 × 30) + 5 = 800 + 1125 - 150 + 5 = 1780 kcal/day

2. Katch-McArdle formula (more accurate if you know your body fat %)

BMR = 370 + (21.6 × lean mass in kg)

This formula is more accurate for muscular individuals because it accounts for actual body composition, not just weight.

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From BMR to TDEE

Once BMR is calculated, multiply it by an activity coefficient to get your TDEE (real caloric needs).

Activity level	Coefficient	Description
Sedentary	× 1.2	Desk job, little to no sport
Lightly active	× 1.375	Sport 1-3x/week
Moderately active	× 1.55	Sport 3-5x/week
Very active	× 1.725	Sport 6-7x/week
Extremely active	× 1.9	Intense sport 2x/day, athlete

Back to the example: if the man trains 4x/week, his TDEE = 1780 × 1.55 = 2759 kcal/day.

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How to optimize your BMR

Good news: you can increase your BMR with a few effective strategies:

• ✅ Build muscle mass: each kg of muscle burns ~13 kcal/day at rest (vs ~5 kcal for fat)
• ✅ High protein intake: high thermic effect (20-30% of calories burned just to digest)
• ✅ Quality sleep: lack of sleep lowers BMR
• ✅ Avoid very restrictive diets: they trigger a downward metabolic adaptation
• ✅ Regular HIIT: "afterburn" effect (EPOC) raises post-workout metabolism

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Limits of formulas

⚠️ All BMR formulas have a ±10-15% margin of error compared to lab-measured metabolism.

For maximum accuracy, you can:

• Get an indirect calorimetry test in a clinic (very precise but costly: $100-200)
• Run a calculated intake for 2-3 weeks and adjust based on real results (weight, performance)

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Key takeaways

BMR is the starting point of any serious nutritional strategy. Calculate it with Mifflin-St Jeor, multiply by your activity coefficient, adjust based on results observed over 2-3 weeks. That is more accurate than any "trendy" diet that ignores your individual physiology. Knowing your metabolism = taking control of your results.