Anthropometry in anorexia nervosa

Abstract

Anorexia Nervosa (AN) is a disorder characterized by a refusal to maintain body weight at or above a minimally normal level for age and height. Two subtypes of the disorder have been identified by the American Psychiatric Association: restricting and binge-eating/purging types. In the former, weight control is attained by a marked reduction in food intake only; in the latter, the occasional food consumption is followed by some forms of compensatory behaviours, such as self-induced vomiting, laxative or diuretic misuse, or strenuous physical exercise. This psychiatric disease mainly involves adolescent girls and young women. Their incidence is increasing in adolescent girls, but first symptoms sometimes appear in childhood. Malnutrition is the prominent feature of AN, requiring a careful and complete medical surveillance, based on anthropometry and body composition assessment. Anthropometric evaluation in AN patients includes the direct determination of some anthropometric parameters (height, weight, skin fold thickness and mid-upper arm circumference) and the calculation of nutritional indices derived from these (BMI and Weight-for-Height). Most single anthropometric measurements, indeed, in themselves may partially assess the nutritional status. Nutritional indices are derived either by combining two or more anthropometric measurements, or by comparing the anthropometric measurements with reference to values of healthy, well-fed populations. The evaluation of body composition completes the anthropometric evaluation and is relevant in these patients, because it gives an objective measure of their malnutrition. These patients, indeed, overevaluate their shape and weight and then have limited motivation to change, which results in unreliable self-evaluation and anamnestic assessment. A wide variety of methods are available to measure body composition. Anthropometry, based on the evaluation of skin fold thickness and midupper arm circumference, represents the simplest method of estimating body composition and, as such, are often used. More sophisticated techniques to study body composition are represented by bioelectric impedance analysis and dual-energy X-ray absorptiometry, both employed in clinical practice as well as in research settings. Other methods, employed only in research settings, are represented by total body imaging techniques (magnetic resonance imaging and computed tomography), underwater weighing, isotope dilution techniques and neutron activation analysis.