Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform essential life functions at rest, such as breathing, circulation, and maintaining body temperature. It represents about 60–70% of your daily energy expenditure.

🌍 Definition

• BMR: The energy (calories) your body uses at rest in a neutral environment, after fasting.
• Reference Point: Measured under strict lab conditions—awake, calm, post-absorptive (12–14 hours after last meal).
• Difference from RMR: Resting Metabolic Rate (RMR) is similar but includes low-effort daily activities, making it slightly higher.

🔑 Factors Affecting BMR

• Body size & composition: More lean muscle tissue → higher BMR; fat tissue requires less energy.
• Sex: Males generally have higher BMR due to larger body size and muscle mass.
• Age: BMR decreases with age, mainly due to muscle loss.
• Genetics & race: Genetic variation influences metabolic rate.
• Hormones: Thyroid hormone levels strongly affect BMR (hyperthyroidism ↑, hypothyroidism ↓).
• Environment: Extreme cold or heat increases BMR as the body works to regulate temperature.
• Life stages: Growth, pregnancy, and lactation raise BMR significantly.

📊 Average Values

• Men: ~1,696 calories/day.
• Women: ~1,410 calories/day.
  These are averages; individual BMRs vary widely.

🧮 How to Calculate BMR

Common equations include:

• Harris-Benedict Equation:
  • Men: (BMR = 88.362 + (13.397 \cdot W) + (4.799 \cdot H) – (5.677 \cdot A))
  • Women: (BMR = 447.593 + (9.247 \cdot W) + (3.098 \cdot H) – (4.330 \cdot A))
    Where (W) = weight (kg), (H) = height (cm), (A) = age (years).
• Mifflin-St Jeor Equation (more accurate for modern populations):
  • Men: (BMR = 10W + 6.25H – 5A + 5)
  • Women: (BMR = 10W + 6.25H – 5A – 161).

In short: Basal Metabolic Rate is the baseline energy your body requires to sustain life, influenced by muscle mass, age, sex, genetics, and environment, and typically calculated using equations like Harris-Benedict or Mifflin-St Jeor.