Obesity and the Body Mass Index

Obesity can be described as an abnormal storage of excess body fat. Excess body fat can be seen around the abdomen of obese men and women or even children. A person with an excess body fat is at risk of developing certain health conditions:

* High blood pressure

* Heart disease

* Diabetes

* Cancer

* Arthritis

* Sleep Disturbances

The body mass index or the BMI is a useful tool to assess overweight and obesity. The BMI is a measurement of person's weight in relation to their height. It is given by the formula weight in kilograms divided by the square of the person's height in meters.

BMI= Weight in kilograms/ Height in metres squared.

If a person's weight is 67kg and height is 1.57 meters, then the BMI is calculated as:

1.57 x 1.57 = 2.46

Then we divide 67 by 2.46 which is 27.2

A person weighing 90 kg with a height of 1.59 will have a BMI of 35.7

Such a person is said to be obese.

The Body Mass Index

16-19 Underweight, 20-25 Normal, 26-30 Overweight, 31-40 Obese, >40 Seriously Obese

The BMI is not applicable for certain groups of people such as:-

* Children or adolescent under 18 years of age

* Pregnant or breastfeeding women

* Athletes who have higher proportion of muscle mass

* The elderly

For children, the BMI is only a screening tool to identify weight problems. In order to diagnose obesity in children, further assessments need to be carried out. These tests may include family history, diet, physical activity and also skin fold thickness.

Weight gain is expected in pregnant women due to the growing fetus, the placenta and other organ involvement. Women with a high BMI before pregnancy,must take care not to gain weight excessively, putting them at risk of developing gestational diabetes, high blood pressure and other health conditions.

The BMI can be misleading for athletes. The BMI does not take into account for muscle mass. Muscle mass is denser than fat and weighs more. A more accurate tool for assessing the BMI is by using other methods such as underwater weighing and measuring skin fold thickness.

With the elderly due to the aging process, height is lost. This means that the BMI will increase without any increase in weight. Also, obtaining accurate height may be difficult due to osteoporosis or other bone deformities such as kyphosis or scoliosis.