Nutritional Status Evaluation: Body Composition and Energy Balance

Nutritional status is the result of our lifestyle over the long term and a major determinant of our health. The balance between energy we ingest as food and energy we expend in the course of physiological processes during our daily activities defines our body composition, a key component of nutritional status. A positive energy balance is at the base of overweight and obesity, where a generalized or a central increase in fat mass is associated with a higher cardio-metabolic risk. In order to plan an effective dietary intervention, we need to know the current body composition in terms of fat mass and fat-free mass and the basal metabolic rate, that is, the energy expenditure at rest in the postabsorptive state. Basal metabolic rate can be assessed by estimate equations or measured by calorimetry. Body composition can be measured or estimated in the field, at the bedside or clinic, or in the laboratory. Anthropometry, body impedance assessment, dual X-ray absorptiometry, and imaging techniques like computed tomography and magnetic resonance imaging are more commonly used in the clinical settings, while densitometry and dilution methods are typical laboratory methods. Information on body composition and energy expenditure represent a powerful tool available to the health-care worker who deals with nutrition for the prevention or treatment of obesity-associated cardio-metabolic diseases.