How does muscle mass affect resting metabolic rate?

Skeletal muscle is metabolically active, requiring 6–10 kcal per pound per day at rest. Therefore, a person with more lean mass, such as 72.6kg (160 lbs) versus 59kg (130 lbs), has a higher resting metabolic rate, potentially differing by 180–300 kcal per day (caution: such aggressive deficits trigger adaptive thermogenesis — a moderate 300-500 kcal deficit is safer and more sustainable). While muscle mass contributes to metabolic variation, it is not the primary factor in weight differences between lean and non-lean individuals.