Low body fat in a human body is often associated with increased health benefits and attractive physical features in both sexes. The human body consists of different lean tissues such as muscle, bone, and organs that are metabolically active and adipose tissues such as fat that are less active. As per medical studies, the healthiest percentage of body fat for males is five percent, whereas for females it is twelve percent. However statistics indicate that on average males have 15 to 18 percent body fat and women have 22 to 25 percent. Low body fat does not determine whether a person is overweight or underweight. A professional bodybuilder may be overweight according to his height, but his body has very little fat and most the extra weight is in lean muscles. On the other hand, other professional athletes such as marathon runners are normally underweight and have very little percentage of body fat. In both the cases, the body fat is more or less the same, but one is overweight and the other is underweight, which proves that body fat does not determine the obesity or leanness of an individual. Although hereditary factors do affect the composition of body fat in an individual, it is often a combination of hereditary factors and lifestyle. After the age of sixteen body fat composition changes are mostly due to changes in fat cell size and not due to the number of fat cells.