Alterations in body composition during adolescence

Abstract

The measurement of body composition has become important in clinical endocrinology and endocrine research because often it is necessary to assess the metabolic effects of hormones on bone, adipose, and lean tissues. All human body composition methods are based on prediction models that indirectly estimate the true body composition with various amounts of error. Prediction error can be minimized if the investigator understands the assumptions of each model. When the assumptions are violated, large errors of estimation may occur. Accurate body composition assessments are difficult to achieve during puberty. For instance, despite its popularity as a clinical body composition model, dual-energy x-ray absorptiometry has not been shown to accurately predict the body composition of children and adolescents. The measurement of total body water to estimate the body composition of children is often used inappropriately because the investigator assumes that the fat-free mass of a child has a proportional water content equivalent to that of an adult. This article reviews the assumptions and validity of body composition models commonly used in endocrinology. As highlighted in a review of recent research on the relationships between body composition and leptin, growth hormone, and insulin resistance, inaccurately estimating the body composition makes it difficult to describe precisely the relationship between body composition and hormone release or the metabolic effects of hormone therapy. The use of inaccurate body composition models also makes it difficult to compare the results of various studies.