Why the Mifflin-St Jeor equation replaced Harris-Benedict
The original Harris-Benedict equations systematically overestimated measured resting metabolic rate in modern subjects by 5–15%. The Mifflin-St Jeor equations were developed specifically to address this, using indirect calorimetry as the reference standard.
A 2005 comparison by Frankenfield et al. tested five prediction equations against measured RMR in 200 subjects and found Mifflin-St Jeor correctly predicted within 10% in 82% of cases, versus 64% for Harris-Benedict. The American Dietetic Association recommends it as the preferred equation for estimating RMR in healthy adults.