Final answer:
Lean body mass is directly proportional to metabolic rate, with more lean muscle contributing to a higher BMR. Gender, age, exercise, and genetics are key factors influencing this relationship, with regular physical exercise being effective in increasing metabolic rate by building lean muscle.
Step-by-step explanation:
The relationship between lean body mass and metabolic rate is significant because lean body mass, which includes muscles, is more metabolically demanding than fat tissue. This means that individuals with a higher proportion of lean muscle mass will have a higher basal metabolic rate (BMR). As a person's lean body mass increases, their metabolic rate increases, allowing them to burn more calories even at rest.
Several factors affect this relationship: age, gender, and genetics. For example, typically males have more lean muscle mass than females, lending to a higher BMR. Similarly, as a person ages, their metabolism can slow by as much as 5 percent per year, primarily due to loss in lean muscle mass. Physical exercise influences this equation by not only burning calories but also helping to build additional lean tissue, raising BMR as a result.
It's important to understand that metabolism isn't static. It adjusts to various factors, including changes in energy intake and levels of physical activity. For instance, when someone over-eats or under-eats, the body adjusts its metabolic rate to partly compensate for the change in food intake. Furthermore, while exercise does increase metabolic rate because of heat transfer and work, living systems, including the human body, do not operate in thermal equilibrium.