Body Mass Index

Body Mass Index (BMI) is a tool used to determine an individual's optimum body weight. It is essentially the relationship between a person's weight and height. The simple formula used to calculate it is:

BMI= (Weight in Kilograms) / (Height in meters squared)

This measure--also known as the Quetelet Index--was developed around 1830 and is attributed to a Belgian named Adolphe Quetelet.

Generally, a BMI of 20 to 25 is considered healthy. A BMI of less than 20 suggests an individual is underweight, while 25 to 29 indicates an overweight person. An index of 30 and above is a sign of obesity.

BMI provides an estimation of fat content in a person's body. Although research has confirmed a strong correlation between fat content and BMI, results may vary from group to group. For instance, athletes may develop significantly higher muscle mass. Muscle contributes more to overall weight than fat. As a result, their BMI may be higher than average despite a lower fat content. Conversely, elderly people who have suffered some deterioration of muscle mass may have lower BMI with higher fat content.

Higher BMI is linked to increased risk of disease and death. Persons with a BMI of 25 to 29 have a higher risk of coronary heart disease, strokes, type 2 diabetes, hypertension (high blood pressure), sleep apnea and respiratory problems, high LDL (bad) cholesterol and low HDL (good) cholesterol. Some cancers, such as endometrial, breast and colon, have also been linked to being overweight. The risks of these diseases and death are magnified in the 30+ BMI category.

BMI is just one of the predictors of health problems and must always be used in conjunction with other indicators. For instance, body shape has also been shown to be a predictor of disease risk. Fat concentrated around the abdominal area (apple shaped body) is considered less healthy than a similar mass of fat concentrated around the buttocks and hips (pear shaped body). BMI also needs to be interpreted differently for different groups such as children and pregnant and nursing women.

Electrical impedance tests or fat fold measures are more accurate means of physically measuring body fat than BMI. However, they all involve a visit to the gym or doctor's office. BMI has the huge advantage of simplicity; anyone can calculate it in the comfort of their own home. It is extremely useful in monitoring one's weight as long as one remembers its limitations.

Ideal Weight | Body Mass Index | Body Fat Testing | Target Heart Rate