Calculating Metabolic Rate

by

Basal Metabolic Rate (BMR) Calculator

Male Female
function calculateBMR() { var gender = document.getElementById("gender").value; var weight = parseFloat(document.getElementById("weight").value); var height = parseFloat(document.getElementById("height").value); var age = parseFloat(document.getElementById("age").value); var bmr = 0; if (isNaN(weight) || isNaN(height) || isNaN(age) || weight <= 0 || height <= 0 || age <= 0) { document.getElementById("result").innerHTML = "Please enter valid positive numbers for all fields."; return; } if (gender === "male") { bmr = 88.362 + (13.397 * weight) + (4.799 * height) – (5.677 * age); } else if (gender === "female") { bmr = 447.593 + (9.247 * weight) + (3.098 * height) – (4.330 * age); } document.getElementById("result").innerHTML = "Your Basal Metabolic Rate (BMR) is: " + bmr.toFixed(2) + " kcal/day"; }

Understanding Basal Metabolic Rate (BMR)

Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform its essential life-sustaining functions, such as breathing, circulation, cell production, nutrient processing, and temperature regulation, while at rest. It represents the energy your body expends at complete rest, in a temperate environment, and in a post-absorptive state (meaning your digestive system is inactive, typically 12 hours after your last meal).

Think of BMR as the energy cost of simply existing. It's a crucial component of your total daily energy expenditure (TDEE). Your TDEE is the total number of calories you burn in a day, including your BMR, the thermic effect of food (calories burned digesting food), and calories burned through physical activity.

Factors Influencing BMR:

  • Gender: Men generally have a higher BMR than women due to typically having more muscle mass and less body fat.
  • Body Composition: Muscle tissue is more metabolically active than fat tissue. Individuals with more muscle mass will have a higher BMR.
  • Age: BMR tends to decrease with age, primarily due to a loss of muscle mass.
  • Body Size and Shape: Larger individuals generally have higher BMRs than smaller individuals because they have more tissue to maintain.
  • Genetics: Individual genetic makeup can play a role in metabolic rate.
  • Hormonal Factors: Thyroid hormones, in particular, significantly influence metabolic rate.
  • Environmental Temperature: Extreme temperatures can increase BMR as the body works to maintain its core temperature.

How is BMR Calculated?

Several formulas exist to estimate BMR. The most commonly used are the Harris-Benedict equation (original and revised) and the Mifflin-St Jeor equation. This calculator uses the Mifflin-St Jeor equation, which 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

Understanding your BMR can be a valuable tool for managing your weight and overall health. It helps in setting appropriate calorie intake goals, whether for weight loss, weight maintenance, or weight gain, when considered alongside your activity level.

Leave a Comment