Identifying a Healthy Weight

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There are a number of ways to determine if you are at an ideal weight. One way is the Body Mass Index (BMI), which is used to estimate your total amount of body fat. It is calculated by dividing your weight in kilograms by your height in metres squared (m2). BMI is an approximate measure of the best weight for health only.

Differences in BMI between people of the same age and sex are usually due to body fat. However, there are exceptions to this rule, e.g. BMI calculations will overestimate the amount of body fat for body builders, some high performance athletes and pregnant woman. They will also underestimate the amount of body fat for the elderly and people with a physical disability who are unable to walk and may have muscle wasting.  BMI is also not an accurate indicator for people with eating disorders like anorexia nervosa or people with extreme obesity.

To calculate your BMI, you need to know:

• Your weight in kilograms
• Your height in metres.

For adults over 18, a healthy BMI is between 18.5 and 25. A result below 18.5 indicates that you may be underweight. A figure of or above 25 indicates that you may be overweight.

Another way of determining if your weight may be putting your health at risk is through waist circumference. This can be a better predictor of health risk than BMI. Having fat around the stomach regardless of your body size, means you are more likely to develop certain obesity-related health conditions. Fat predominantly deposited around the hips and buttocks doesn’t appear to have the same risk. Men, in particular, often deposit weight in the waist region (what many refer to as beer gut or pot belly!).

Studies have shown that the distribution of body fat is associated with an increased prevalence of diabetes, hypertension, high cholesterol and cardiovascular disease.

Generally, the association between health risks and body fat distribution is as follows:

• Least risk – slim (no pot belly)
• Moderate risk – overweight with no pot belly
• Moderate to high risk – slim with pot belly
• High risk – overweight with pot belly

Waist circumference can be used to indicate health risk.

For men:

• 94cm or more – increased risk
• 102cm or more – substantially increased risk

For women:

• 80cm or more – increased risk
• 88cm or more – substantially increased risk