Metabolic rate is measured by assessing the amount of energy the body expends at rest and during physical activity. This can be done through methods such as indirect calorimetry, which measures oxygen consumption and carbon dioxide production during specific conditions. Additionally, factors like age, gender, body composition, and fitness level can influence metabolic rate. Understanding metabolic rate is essential for devising effective weight management and nutrition plans, as it provides insight into how efficiently the body burns calories and utilizes energy.