Calculating BMR - Basal Metabolic Rate

The most accurate equation for calculating BMR is the Mifflin-St Jeor equation:

Males: BMR = 10 × weight (kg) + 6.25 × height (cm) - 5 × age (years) + 5
Females: BMR = 10 × weight (kg) + 6.25 × height (cm) - 5 × age (years) - 161

This equation has been shown to be more accurate than the older Harris-Benedict equation. It takes into account the person's weight, height, age, and sex to provide a personalized BMR estimate.

Here are some other factors that might effect BMR:

• Body composition: Individuals with more muscle mass tend to have a higher BMR.

• Age: BMR typically decreases by 2-5% per decade after age 40 as muscle mass declines.

• Sex: Men generally have a higher BMR than women due to greater muscle mass.

• Hormones: Thyroid hormones, growth hormone, and sex hormones can impact BMR.

• Genetics: Some people are predisposed to having a higher or lower BMR.

• Illness/stress: Conditions like fever, injury, and emotional stress can temporarily increase BMR.

NOTE: It's important to note that BMR calculations, even using the most accurate equations, will not be perfectly precise. There is still about 26% unexplained variance in BMR between individuals, even when controlling for known factors.

Adjustments for old adults and middle-aged adults

The Mifflin-St Jeor equation was developed and validated primarily on younger and middle-aged adults, so its accuracy may be lower for older adults.

Use the Cunningham equation, which was developed specifically for older adults (aged 60-94 years)

BMR (kcal/day) = 500 + 22 × Fat-Free Mass (kg)

Ethnic Minorities

Owen equation for African Americans and the Henry equation for Asian populations.

However, one study found the Owen equation predicted BMR with appropriate accuracy for African American women, but not for European Americans

BMR (kcal/day) = 795 + 7.18 × Weight (kg)

The Henry equation was developed specifically for Asian populations:

BMR (kcal/day) = 10.4 × Weight (kg) + 615 × Height (m) - 282 × Age (years) + 35 for males
BMR (kcal/day) = 9.4 × Weight (kg) + 726 × Height (m) - 422 × Age (years) + 8.7 for females

Source

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References:

Common Prediction Equations Overestimate Measured Resting Metabolic Rate in Young Hispanic Women - NCBI - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3779143/