For decades, official guidance has decreed that the way to find out if you’re a healthy weight is by measuring your BMI.
The calculation takes into account your height and weight, and then tells you whether you're underweight, healthy, overweight or obese.
The BMI measurement was first created in the 1800s by a Belgian mathematician called Adolphe Quetelet. By the late 1900s, it had been adopted by governments across the world as a way for people to work out if they were over- or underweight.
Calculated from a person's height and weight, BMI breaks down into four categories:
- Underweight: BMI below 18.5
- Normal: BMI ranging between 18.5 and 24.9
- Overweight BMI between 25 and 29.9
- Obese: BMI of 30 or higher
But how useful is this number really?
Last year, a study by UCLA concluded that tens of millions of people who had overweight and obese BMI scores were in fact perfectly healthy.
But they also found that 30 per cent of people with “healthy” BMIs were in fact not healthy at all based on their other health data.
So, what’s going on?
There is a myriad of reasons why BMI isn’t as accurate a measure of health as many of us were brought up to believe, but one of the main ones is that BMI can’t distinguish between fat and muscle.
A pound of fat takes up a much larger volume on the body than a pound of muscle, even though they of course weigh the same. (Muscle is about 18 per cent denser than fat.)
As a result, many incredibly fit, athletic, muscular people are labelled “overweight” by their BMI.
I believe it is only of any use when looking at large populations of people to get an idea of trends. “It should not be used on a individual basis,”
BMI measurements are too broad and it assumes one size will fit all, when this simply isn’t the case.
So take and example of two different ladies.
“One of them is very active with a low percentage of body fat and a high percentage of muscle mass, the other sedentary with a high percentage of body fat and a low percentage of muscle mass.”
Both women can come out with the same BMI, despite having drastically different body compositions.
Another problem with BMI is that it doesn’t measure or take into account where on the body fat is carried. One person could have skinny legs and carry a lot of fat around their middle, whilst another could have the same amount of fat spread around their body.
Both may have the same BMI, but the former person would be at a higher risk health-wise.
Visceral fat around your organs is particularly dangerous, but it’s possible to have a lot and still come out with a healthy BMI.
This has led many people to argue that a far more important measurement is your hip to waist ratio. According to the World Health Organisation, this should be no more than 0.85 for women and 0.9 for men.
It’s crucial to look at where your fat is placed, as too much around the midsection is cause for concern.
Overall though, BMI is more often a problem than a reliable measure of health.
“I think other methods should be used to measure an individual's health as it often rides on so much more than a number,” Focus on Body Fat Percentage, Lean Muscle Mass and your hip to waist ratio for an Accurate picture of your progress.
If you want to know whether you’re in good health or not, there are endless aspects to consider. But it’s probably best not to see your BMI as the be all and end all - there’s a lot more to it than that.
Next Week’s Blog I will be elaborating on this and demonstrating how best to take these measurements.