"In the frontispiece to their book on human physique, Sheldon et al. (1940) showed photographs of three extremes of somatotype: an endomorph, who was characterized by pendulous fat deposits; a mesomorph, who looked well proportioned and muscular; and an ectomorph, who looked like a victim of anorexia nervosa. There can be little argument about which of these three types would make a suitable soldier. Without question, the massively obese endomorph would be unable to perform physically, would fail even the most subjectively lenient standards of military appearance, would likely encounter acute as well as long-term health problems as a direct consequence of excess fat, and would suffer miserably with work in even a moderately hot environment. At the other extreme of size, the ectomorph would be unable to carry a normal load on a standard road march task, would likely suffer health problems from extreme deficiency of muscle mass, and would be unable to effectively thermoregulate in a cold environment. The current Army body composition standards ignore the ectomorph, because this soldier is undetected by the height-weight screening tables, even when the soldier is so deficient in fat-free mass that relative body fat is high. This omission is a change from the earlier standards, which emphasized the exclusion of physically weak individuals who would have difficultly with basic soldier tasks. At the upper end, the endomorph is clearly excluded by current Army standards, as are many individuals who may even approach the mesomorph in appearance and physical capabilities. Thus, the second change from previous standards is that current body fat standards draw a precise line, without confidence intervals, for acceptable fatness; these standards take into account neither the strength of the association between body fat and military performance nor the reliability of the method of estimation. Previously, a physician made the final subjective determination that a soldier was unsuited to the Army because of his or her obesity, but this was subjective and had little impact on offenders of military appearance. Without this buffer, the arbitrary standards have had a major impact. Thus, it becomes more important to test and carefully adjust body composition standards to performance end points to ensure that good soldiers are not eliminated."