As dieticians, we have been using the measure of body mass index (BMI), for many years, as one of the indicators which tell us whether patients are at a healthy weight or not. BMI is measure by dividing your weight in kilograms, by your height, in meters squared i.e.

Weight (kg’s)

Height (m²)

This number is then compared to the range that is considered healthy (18.5 – 24.9). If you are below this number, you are considered underweight. If you are in the range of 25-29.9, you are considered overweight. A BMI of between 30- 34.9, puts you at Obese, Class 1, and if you sit between the range of 35- 39.9, you are classified as being Obese, Class 2. A BMI of greater than 40, puts you in Obese Class 3.

With obesity on the direct rise in South Africa, so are non-communicable diseases (NCD’s), such as metabolic syndrome, type 2 diabetes, and hypertension. We are therefore always looking ways in which we can improve our health, and also how to measure that improvement. Being within the normal BMI range is one of the goals that many wish to achieve.

The main problem with the BMI, is that it gives no indication of body composition, or fat distributions. BMI also does not differentiate between men and women. Many people who are above the normal BMI range have no signs of high blood glucose, and display a normal blood pressure. Many people within the normal BMI range, display symptoms of the onset of Diabetes and Hypertension, and these are often referred to as chronic diseases of lifestyle.

Age should also be considered. Many overweight and obese people do not show any signs of the onset of NCD’s, and this could be the case if they are young and their age is therefore in their favor. However, it does not mean that they could not later develop some of these chronic diseases of lifestyle.

With these discrepancies, it is therefore becoming more precedent to consider other indicators, when establishing the overall good or bad health of a patient.

Fat percentages, and fat distribution are two essential indicators to take into consideration when determining health.

Men and women require different amounts of body fat, when compared to each other, and also when compared at different life stages. Women require more fat, as this is linked to hormone regulation, the presence of breast tissue, etc.

Central obesity, is when a person carries the majority of his or her fat, around the middle of the body. This is a strong negative indicator for health, and can increase the risk of developing Type II Diabetes, and Hypertension.

The reason that BMI became such a popular and standard measurement of health, is because it is one of the most simple measure to perform. Measuring body fat, previously required the use of calipers, which often allowed too much room for human error, even when used by a medical professional.

Body stat measurements are now the gold standard, but are not always available, and can be expensive.

One measure that could be more frequently included is the measure of waist circumference, as this could easily show the extent of any central obesity. Taking this measurement is as easy as weighing and measuring the height of an individual, and can be done using a simple measuring tape.

In conclusion, BMI should be used in conjunction with body fat percentages, as well as waist circumference measurements, when determining the health of an individual. Age and gender should also be noted.


Written by:

Ashley Gibbon