What physiological effect does increased muscle mass have on the body?

Increased muscle mass has a significant positive impact on the body, particularly by enhancing energy expenditure. Muscle tissue is metabolically active, meaning it requires energy (calories) to maintain itself, even at rest. Therefore, individuals with greater muscle mass tend to have a higher basal metabolic rate, which leads to increased overall energy expenditure. This effect can support weight management by burning more calories throughout the day, even when not exercising.

The other options do not reflect the physiological effects of increased muscle mass. For example, decreased metabolism contradicts the well-established understanding that more muscle leads to a higher metabolic rate. Additionally, while increased muscle strength can reduce the perception of fatigue during physical activities, it does not inherently increase fatigue overall. Finally, increased muscle mass typically improves mobility rather than decreases it, as stronger muscles facilitate better movement and support joint stability.