The relationship between activity level and metabolic rate is direct; increased physical activity typically raises metabolic rate, leading to higher energy expenditure. Metabolic rate refers to the rate at which the body converts food into energy, with basal metabolic rate determining energy needs at rest. Regular exercise can enhance muscle mass, which in turn boosts metabolic rate even when at rest, promoting weight management and overall health. Understanding this relationship is essential for optimizing fitness and well-being strategies.