The role of the basal metabolic rate (BMR) in energy expenditure is to represent the minimum amount of energy required to maintain essential physiological functions while at rest. BMR accounts for calorie usage in processes such as breathing, circulation, and cell production. It serves as a foundation for calculating daily caloric needs, influencing weight management and dietary planning. Factors such as age, sex, muscle mass, and hormonal levels can affect BMR, indicating its significance in metabolism and personal health assessments.