The largest component of the body is water, accounting for about 50% - 60% of body weight, followed by fat. The rest are proteins and sugars contained in muscles, and inorganic substances contained in bones.

Body fat percentage refers to the ratio of fat mass in the human body to body weight.

The body fat percentage of boys is about 17-23%, and that of girls is about 20-27%. Boys under 30 years old have a body fat percentage of 14-20%, and boys over 30 years old have a body fat percentage of 17-23%. Girls under 30 years old have a body fat percentage of 17-24%, and girls over 30 years old have a body fat percentage of 20-27%. The average BMI value of boys is about 20-25%, and that of girls is about 19-24%.