Body Mass Index (or BMI) is basically the mathematical calculation of your body weight divided the square of your height.
It is used as an indicator of whether you are underweight, normal weight, overweight or obese.
A BMI of less than 18.
5 is underweight, 18.
5-25 is 'normal'.
25-30 is overweight and 30+ is obese.
It can be a useful figure to show progress being made in a weight loss (or weight gain) effort and it is motivating to see your BMI creeping towards the 'healthy' zone.
However BMI figures can be misleading and some athletes would be classed as obese by using this calculation as BMI takes into account only weight and height and not what the weight is actually made up of.
Therefore you could be extremely muscular and very fit, but could be heavy because of this.
Measuring your body fat percentage instead of your BMI is a much more accurate indication of how healthy you are.
Especially if you are combining a weight loss programme with exercise, some weeks you may not lose weight but you will have lostfat as you are converting some of that fat into muscle through the exercise you are doing and muscle weighs more than fat.
They may also be some people who have a healthy BMI and look like a healthy weight, but if they got their body fat percentage measured may actually be over-fat even though they are a healthy weight! This is because some people store a lot of fat internally, around their organs, but this may not show outwardly.
So measuring you BMI can be a helpful indicator of progress being made if you are obviously overweight, but a regular body fat percentage reading will give you a much more accurate picture of the changes taking place in your body.
Body Fat readings can be taken in a number of ways - by purchasing a pair of scales with this facility or a dedicated Body Fat Monitor or at the gym or by your doctor.
If you do not have the facility to test your body fat then you can always keep track of your measurements - waist, hips, bust, arms, thighs etc.
This is a good way to see if you are losing inches and can be a good motivational tool if you don't lose weight one week but you do see yourself shrinking regardless.
There is also an online body fat test but this will not be as accurate as getting it measured by a professional or with an electronic body fat monitor.