A normal body mass index, or BMI, for both women and men is between 18.5 and 24.9, according to the Centers for Disease Control and Prevention. For adults over the age of 20, body mass index is calculated based upon an individual's height and weight.
There is a strong correlation between BMI and body fat, however this relationship can vary by race, age and gender, states the CDC. Women tend to have a higher percentage of body fat than men at the same body mass index. Increased muscle mass, often found in bodybuilders and athletes, rather than elevated body fat may affect the interpretation of BMI calculations.