Understanding BMI
Tracking your Progress

Understanding BMI and waist circumference

Two of the most commonly used and easily measured parameters to determine if a persons’ weight is healthy or unhealthy are BMI and waist circumference. 

Body Mass Index (BMI)

Body Mass Index or BMI is a statistical measurement that is often used to assess the levels of overweight and obesity at a population level. It calculates body weight in relation to height and for most people provides a good indication of total body fat. It is often quoted because of the ease of calculation and non-invasive method of measurement.

It is calculated by:- (calculate my BMI now)

weight (kg)
height (m) x height (m)

Why is BMI important?

Having a BMI outside the healthy or normal weight range, has been shown to put you at increased risk of health conditions such as diabetes, heart disease and stroke. As shown in the table below, the health risks associated with excess weight increase dramatically with increasing BMI. 

classification BMI (kg/m2) risk of co-morbidities and related disease
underweight less than 18.5 low (but possibly increased risk of other clinical problems)
normal range 18.5 to 24.9 average  (no increased risk)
overweight 25.0 to 29.9 increased
obese I 30.0 to 34.9 moderate
obese II 35.0 to 39.9 severe
obese III 40.0 or greater very severe

Do you need to reduce your BMI?

If your BMI is putting your health at risk there are some immediate actions you can take to reduce your BMI to a healthier range.

  • take KicStart™ VLCD twice a day. With less kilojoules than a regular meal your body will use your stored fat for energy so you can start losing weight immediately
  • get familiar with the keys to success and try and include these in your every day routine for better healthy living. 

Limitations of using BMI calculations

There are limitations to the use of BMI calculations.  When looking at the overall health risk of an individual person, BMI should always be combined with waist circumference measurements because BMI calculations can:

  • Overestimate the amount of body fat for people with proportionally high muscle mass e.g. athletes and people of certain ethnicity (eg Islander populations) and give a false high estimate of relative risk
  • Underestimate the amount of body fat for the elderly & people with a physical disability who may have muscle wasting and give a false low estimate of relative risk.

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Waist Circumference

Waist Circumference is an indication of the abdominal fat of a person. As abdominal fat is associated with significant health risks, this measurement alone provides a good indication of the health risk associated with being overweight.

The waist should be measured at the narrowest part of the torso (between ribs and hips) when looking front-on at your body.

  1. Find a point mid way between the bottom of your lowest rib and the top of your pelvic bone.
  2. Stand comfortably with your feet approximately 20 – 25 cm (10 to 12 inches) apart.
  3. Fit the tape measure snugly around your waist without compressing any of the underlying soft tissue.
  4. Measure to the nearest ½ cm at the end of a normal breath out.

Waist circumference has been consistently shown to be closely related to an increased risk of diseases such as cardiovascular disease and type 2 diabetes:-

waist circumference (cm)
risk of metabolic complications men women
increased 94 cm or more 80 cm or more
substantially increased 102 cm or more 88 cm or more


Do not become obsessed with your scales!! Many factors other than the dreaded number on the scales contribute to the potential health impacts of being overweight. And some people will naturally lose more than others depending on their muscle mass and certain metabolic differences.

By all means have your healthcare professional measure your weight (or do it yourself) at the start of any lifestyle program, but don't be fastidious about the loss in weight. Look at changes in waist circumference or clothing sizes as these will change quicker than actual weight, especially if you are exercising more and therefore building muscle as you lose fat.

And remember, this time it IS about good health - and not just dropping kilos. There are more reasons than just cosmetic ones as to why we should all manage our weight – a healthy weight will help you maintain a healthy body and a healthy mind.

As with any health care plan, it is really beneficial if you have a healthcare professional help you with measuring and recording the progress of your healthy weight plan. Not only are they able to help you set some goals, but they can be a great support in times when you need them most. Invest in the confidence of someone you can trust to help you with one of the biggest changes of your life!

Other benefits of a healthy weight

Some of the other ways you can assess the benefit of your weight loss are:

  • Decrease in blood pressure OR
  • Improved blood glucose levels OR
  • Improved cholesterol and triglycerides OR
  • Your doctor reducing or stopping some of your medications
    (REMEMBER – don’t adjust your medication yourself always discuss any changes to your medication
    with your doctor first) OR
  • Increased energy OR
  • Improvements in personal body image and sense of wellbeing OR
  • Decreased snoring OR
  • Less joint or muscle pain

Losing weight can lower your blood pressure, your blood sugar and / or cholesterol levels so if you have these conditions, or are taking any medications regularly for ongoing medical conditions, you will need to let your doctor or specialist know before you start losing weight as they will need to monitor you carefully and may need to reduce some of your medications.

Tracking your Progress

We all lead busy lives and unless we make a habit of keeping track of our weight or waist circumference, we often don't notice that our weight has started to increase. However we recommend that you record your weight and waist circumference not more frequently than once each week, to avoid becoming disheartened by natural daily fluctuations.

With consistent self monitoring you will be able to keep yourself on track over the long term by becoming aware of problem behaviour or negative progress as it occurs and to be able to act quickly to implement strategies to improve the situation before you get too far off track.