How the IOM EER equations work
Unlike the Mifflin–St Jeor or Harris–Benedict equations that first calculate a basal rate and then multiply by an activity factor, the IOM EER equations directly incorporate a Physical Activity (PA) coefficient into a single formula. The PA values differ slightly between men and women and reflect four activity categories: sedentary, low active, active, and very active.
The equations were derived from doubly labelled water studies—the gold standard for measuring free-living energy expenditure—making them among the most evidence-based population-level estimates available.