BMI- A Decent Gauge Of "Measuring Body Composition" For Non Athletic Population.

I have seen written and heard lots of people give the BMI a bit of a bashing saying its worthless and dismissing readings. Their argument is it doesn’t distinguish between muscle mass and fat and that muscle is denser than fat.

However……. lets be brutally honest here- the average person is not heavy because they are overly muscular...........!

The BMI is a relatively straightforward and convenient method of assessing someone's weight. The BMI will give you an indication if your weight is appropriate for your height

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To work out your BMI:

• divide your weight in kilograms (kg) by your height in metres (m)
• then divide the answer by your height again to get your BMI

For example:

• If you weigh 70kg and you're 1.75m tall, divide 70 by 1.75. The answer is 40.
• Then divide 40 by 1.75. The answer is 22.9. This is your BMI.

For most adults, an ideal BMI is in the 18.5-24.9 range.
If your BMI is 25 or more, you weigh more than is ideal for your height:

• 25-29.9 is overweight
• 30-39.9 is obese
• 40 or more is very obese

If your BMI is less than 18.5, you weigh less than is ideal for your height.

Generally if  your BMI is 25 or more, you should think about losing weight. Being overweight or obese can increase your risk of health problems

(There is a chart for you at the bottom of the page also for you to see your BMI).

However for athletes and well trained individuals....

For the general population it gives a fairly decent indication of where you are body weight wise. Not perfect but decent. But For athletes and well trained individuals who are lean and muscular BMI is not suited to them and will not be accurate

That is, say we have two individuals who are 6 feet tall and weigh 90kg.  But say one is an athlete and has 10% body fat and the other is not and has 30% body fat.  They will have the same BMI value of 26 but it’s fairly clear that they are not going to be in the same category in  terms of health risk, how they look and fitness levels..  BMI doesn't give a distinction between fat mass and lean body mass and since active individuals typically have more LBM (lean body mass - hence less fat) at any given body weight, BMI is not accurate for them.

BMI has its flaws as it doesn’t indicate between muscle mass and fat or where body fat is stored. However it is quick and easy to use and for the for the average person I think it is a pretty good reflection on where the average person or gym goer is  at body fat wise.

Why.....because in reality you wont see many people who are not training at a good standard carrying lots of muscle mass, have low body fat when their weight is high.

Jamie Miller Personal Trainer
UK Fitness & Personal Training
Aberdeen