Although fat, for the most part, is thought to be an evil commodity, it happens to be required for normal physiological function of the various organs. This form of fat is referred to as "essential fat" or essential fatty acids and combines with other nutrients to form important structural compounds such as blood lipids, steroids, cell membranes, bile and hormones. Women should not have less than 12% body fat and men 5% to meet these "essential fat" needs.
Experts feel that women should stay below 30% body fat and men below 20% in order to decrease risk of chronic diseases. These percentages represent borderline obesity for women and men respectively. Ideally, women should try to maintain a body fat percent between 18%-22% and men between 12%-17%.