Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform its essential functions while at rest. These functions include breathing, circulating blood, regulating body temperature, cell production, and brain activity. Essentially, it's the energy your body expends just to keep you alive and functioning, even if you were to lie in bed all day without moving.
Understanding your BMR is a crucial first step in managing your weight and overall health. While your BMR represents the calories burned at complete rest, your total daily energy expenditure (TDEE) is higher because it includes the calories you burn through physical activity and the thermic effect of food (the energy used to digest and absorb food).
Factors Influencing BMR:
Body Composition: Muscle tissue burns more calories at rest than fat tissue. Therefore, individuals with more muscle mass generally have a higher BMR.
Age: BMR tends to decrease with age, primarily due to a loss of muscle mass.
Sex: On average, men have a higher BMR than women. This is often attributed to differences in body composition (men typically have more muscle mass) and body size.
Genetics: Your inherited genes play a role in determining your metabolic rate.
Body Size and Shape: Larger individuals generally have a higher BMR because they have more tissue to maintain.
Hormonal Activity: Conditions affecting the thyroid gland, for example, can significantly alter BMR.
Environmental Factors: Extreme temperatures can increase BMR as the body works harder to maintain its core temperature.
How BMR is Calculated:
The most common formulas for calculating BMR are the Harris-Benedict equation and the Mifflin-St Jeor equation. The Mifflin-St Jeor equation is generally considered more accurate for most people.
Mifflin-St Jeor Equation:
For Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
This calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate. Knowing your BMR can help you set appropriate calorie intake goals for weight management, whether you aim to lose, maintain, or gain weight.