Basal Metabolic Rate for a 57kg Man
For a 57kg man, the basal metabolic rate is approximately 1,140 kcal/day, calculated using the simplified approach of 20 kcal/kg body weight per day for resting energy expenditure. 1
Calculation Approach
The most straightforward method uses the weight-based estimation of approximately 20 kcal/kg/day for basal metabolic rate in adults. 1 This yields:
- 57 kg × 20 kcal/kg = 1,140 kcal/day
This represents the resting energy expenditure (REE), which differs by less than 10% from true basal metabolic rate (BMR) measured under strict conditions. 1
Alternative Calculation Methods
Harris-Benedict Equation
If using the Harris-Benedict equation (the most validated predictive equation), you need additional parameters: 2
- Formula for men: BEE = 66.4730 + 13.7516 × weight(kg) + 5.0033 × height(cm) - 6.7550 × age(years) 2
- This equation requires height and age data not provided in your question
Lean Body Mass Method
The most accurate single predictor of BMR is lean body mass, using the equation: BMR = 500 + 22 × LBM(kg). 3 However, this requires body composition assessment, which is not typically available in routine clinical practice. 3
Important Clinical Considerations
The 20 kcal/kg estimate represents basal needs only—not total daily energy requirements. 1 To determine total energy expenditure:
- Multiply BMR by physical activity level (PAL): 1.2 for lying awake, 1.4-1.5 for light activity, 1.7 for moderate activity 1
- For a sedentary but ambulatory person: 1,140 × 1.5 = approximately 1,710 kcal/day 4
Age significantly affects metabolic rate—older adults have 13% lower BMR than younger adults due to decreased fat-free mass. 4 Without knowing the patient's age, the 20 kcal/kg estimate provides a reasonable middle-ground approximation. 1
Ethnicity matters for accuracy—current prediction equations overestimate BMR in tropical populations by 8% and in African-Americans compared to Caucasians. 5, 6 Standard equations were developed primarily on Caucasian populations from decades ago. 5