What happens to muscle mass as resting metabolic rate declines?

When the resting metabolic rate (RMR) declines, there is often a correlation with a reduction in muscle mass. This decline in RMR can be caused by several factors, including decreased physical activity levels, aging, and caloric restriction. Muscle is metabolically more active than fat tissue, meaning that a higher muscle mass contributes to a higher RMR.

When RMR decreases, signaling a lower energy expenditure, the body may respond by conserving energy. This is often accompanied by a loss of muscle mass, as the body may prioritize energy for essential functions and reduce muscle tissue, which requires energy to maintain. Additionally, if an individual is not engaging in resistance training or consuming adequate protein, the chances of losing muscle mass increase even further. Consequently, the relationship between a decline in resting metabolic rate and muscle mass loss is well-established in nutritional and exercise science, reinforcing the reasoning behind the correct answer.