Anthropometry involves measuring the physical dimensions of the human body, such as weight and body circumference. Such measurements are important indicators of nutritional status. For infants and children, key measurements include head circumference, chest circumference, weight, length/height, mid-upper arm circumference, and weight-for-age. These measurements are used to identify undernutrition. During pregnancy and adolescence, weight, BMI, and waist circumference are important. For the elderly, weight, height, BMI, waist circumference, and waist-hip ratio are measured but special standards are needed due to changes in body composition with aging.