There’s a lot of talk about the Body Mass Index, or BMI in health and fitness circles. Many health clubs use this as a factor in fitness assessments, but what does it mean, and is it accurate?

There is some debate over the accuracy of this method of assessment, but it still provides a general idea of your health and fitness.

Measuring up

The Body Mass Index is a method of calculating your total body fat, and is used to see if your body weight is in a normal and healthy range. While it doesn’t calculate directly how much body fat you are carrying, it indicates where on the BMI scale you sit. A simple formula for calculating your BMI is dividing your weight in kilograms by your height in metres squared. The formula is BMI=kg/m2. This is only applicable to fully grown adults, and not children. There are specially formulated scales for children, depending on their age, weight and height. You can calculate your BMI yourself, or your fitness club can calculate it during an assessment.

Where you sit on the scale

Once you’ve worked out your BMI, you’ll come up with a number, and where you sit on that scale will determine if you are underweight, overweight or in the healthy range. Anything under 18.5 is considered underweight; if your BMI is between 18.5 and 24.9 is normal and a healthy height/weight ratio for a young to middle-aged adult. 25-29.9 is considered overweight, and anything over 30 is seen as obese. These results of course vary from person to person, and other factors, such as lifestyle, gender, age, smoking, alcohol intake and muscle weight need to be taken into account. Your health centre can give more accurate results with callipers measuring your body fat and waistline.

Health and fitness factors

Health and fitness will play a part in these results. If you are underweight, it may indicate malnutrition, and your fitness instructor will encourage you to gain weight, both fat and muscle. You are also at risk of compromised immune function, respiratory disease, digestive disease, osteoporosis, and fragile or brittle bones. If you are overweight or obese, this could affect your health adversely, and increases the risk of high blood pressure, type 2 diabetes, high cholesterol, heart disease, female infertility and cancer. The good news is that losing even 10 per cent of your weight will directly reduce your BMI. In any case, it’s a good idea to consult a medical professional about appropriate dietary and fitness measures.

Exceptions

The BMI is not a magic tell-all method; it doesn’t differentiate between body fat and muscle mass, so bodybuilders, athletes and regular gym attendees may receive a higher BMI that doesn’t mean they are overweight. People with physical disabilities and limited mobility and people 74 years and older may receive a lower BMI result, and this too doesn’t mean they are underweight.

For more information about the Body Mass Index and health and fitness strategies, contact your local fitness gym. Start your search here: