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)
- 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
- For females:
- Convert to calories: MJ/day x 240 = kcal/day
- 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
- BMR = 0.0342 x 65 + 3.5377 = 5.7607 MJ/day
- 5.7607 MJ x 240 = 1382 kcal/day
- Daily total energy requirement = 1.3 x 1382 = 1797 kcal/day
- Adjusted diet = 1797 – 500 = 1297 kcal/day
- BMR = 0.0342 x 65 + 3.5377 = 5.7607 MJ/day
By calculating your BMR, you can tailor your diet and exercise plans to effectively manage your weight and achieve desired results.