Which factors influence basal metabolic rate (BMR)?

The basal metabolic rate (BMR) is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state, meaning that the digestive system is inactive. It represents the energy needed to maintain basic physiological functions such as breathing, circulation, and cellular production.

The factors that influence BMR include age, sex, body composition, and hormonal levels. As individuals age, BMR typically decreases due to a reduction in lean muscle mass, which is more metabolically active than fat tissue. Men generally have a higher BMR compared to women due to having a larger muscle mass. Body composition plays a significant role; individuals with a higher percentage of muscle mass will have a higher BMR. Hormones, particularly thyroid hormones, significantly impact metabolic rate; an increase in these hormones can elevate BMR, while deficiencies can lead to a decrease.

While other factors like body temperature and hydration levels can have minor effects on BMR, the core influences are more related to physiological characteristics and hormonal regulation, which is why the selected answer encompasses the most significant determinants.