Energy requirement: Factors that influence variation in basal metabolic rate

Basal metabolic rate (BMR) can be simply defined as the minimum amount of energy the body requires at rest and is commonly measured using indirect calorimetry techniques. Factors that can influence metabolic rate can be technical in nature, owing to the limitations and constraints of the precision of the equipment, or can be biological, linked to the physiology and behaviour of the subject. The principles and assumptions of indirect calorimetry are discussed. It is well documented that body size and composition are the main determinants of resting energy requirements, whereas the influence of chronic or acute changes in disease state is less well documented. Aside from the clinical perspective, accurate measurement of BMR is important as it is used in epidemiological or public health nutrition to calculate total daily requirements and to classify energy intakes. Many factors, such as body composition, age, gender, food amount and composition, diseases, medications, hormonal status and genetic differences, can affect the variability in BMR and thus can lead to errors in classification of population data.