What is Basal Metabolism? How Many Calories are Burned Daily?

Basal metabolism refers to the minimum energy required to sustain basic life functions, such as breathing, heartbeat, and maintaining body temperature.

Composition of Daily Total Energy Expenditure

Energy Type	Percentage	Description
Basal Metabolism	Around 70%	Energy needed to sustain vital life activities
Activity Metabolism	Around 20%	Energy consumed by daily living and physical activity
Diet-Induced Thermogenesis (DIT)	Around 10%	Energy used for digesting, absorbing, and metabolizing food

Factors Affecting Basal Metabolism and Energy Consumption by Body Organs

Basal metabolism is primarily influenced by muscle mass—greater muscle mass leads to higher basal metabolism. Additionally, factors such as age and gender affect basal metabolism:

Body Organ	Percentage of Basal Metabolism
Skeletal Muscle	Around 38.0%
Liver	Around 12.4%
Digestive System	Around 7.6%
Kidneys	Around 7.5%
Spleen	Around 6.3%
Heart	Around 4.4%
Brain	Around 3.0%
Others	Around 20.8%

Impact of Age and Gender on Basal Metabolism

Basal metabolism gradually declines with age, especially after the age of 40. Women generally have lower basal metabolism compared to men due to higher body fat and lower muscle mass.

Age (years)	Male Basal Metabolic Standard (kcal/kg/day)	Male Basal Metabolism (kcal/day)	Female Basal Metabolic Standard (kcal/kg/day)	Female Basal Metabolism (kcal/day)
18~29	24.0	1550	23.6	1210
30~49	22.3	1500	21.7	1170
50~69	21.5	1350	20.7	1110
70+	21.5	1220	20.7	1010

Calculation of Basal Metabolic Rate (BMR)

1. Calculate daily energy requirement (MJ/day):
   • For females:
     • 18–30 years = 0.0621 x Weight (kg) + 2.3075
     • 31–60 years = 0.0342 x Weight (kg) + 3.5377
     • 60+ years = 0.0377 x Weight (kg) + 2.7545
   • For males:
     • 18–30 years = 0.0630 x Weight (kg) + 2.8975
     • 31–60 years = 0.0484 x Weight (kg) + 3.6534
     • 60+ years = 0.0491 x Weight (kg) + 2.4587
2. Convert to calories: MJ/day x 240 = kcal/day
3. Calculate daily total energy requirement: BMR x Activity Factor
   • Low activity: 1.1 x BMR
   • Moderate activity: 1.3 x BMR
   • High activity: 1.5 x BMR

Example Calculation

• 36-year-old woman, 65 kg, moderate activity
  1. BMR = 0.0342 x 65 + 3.5377 = 5.7607 MJ/day
     • 5.7607 MJ x 240 = 1382 kcal/day
  2. Daily total energy requirement = 1.3 x 1382 = 1797 kcal/day
  3. Adjusted diet = 1797 – 500 = 1297 kcal/day

By calculating your BMR, you can tailor your diet and exercise plans to effectively manage your weight and achieve desired results.

本文為疾病衛教資訊，非藥品廣告，不涉及特定藥品之推介或販售。