Metabolic rate is measured by assessing energy expenditure, typically using methods like indirect calorimetry. It reflects the number of calories the body burns at rest and during activity. Several factors influence metabolic rate, including age, gender, genetics, and body composition. Muscle mass significantly impacts the rate since muscle tissue burns more calories than fat. Additionally, hormones, nutritional intake, and physical activity levels also play crucial roles. Understanding these factors can help individuals optimize their metabolism for weight management and overall health.