The BMI, or body mass index, is used to assess a person's appropriate weight range based on their height. BMI is useful for assessing risk because waist circumference measures the quantity of central fat. Photo by Anna Shvets from Pexels For most persons above the age of 18, the BMI is a helpful assessment. However, it is merely a guess, and it does not account for factors such as age, race, gender, or body composition. An increase or reduction in BMI can have a major impact on physiology at the cellular level. Insulin resistance, inflammatory states, and cognition have all been linked to BMI in studies. Classification and Definition of BMI BMI, or body mass index, is a statistical indicator that uses a person's weight and height to calculate body fat in males and females of any age. BMI = weight (in kg)/ height2 (in m2) is determined by dividing a person's weight in kilograms by their height in meters squared. The individual's BMI number is then calculated using