Nourish on.... BMI (Body Mass Index)

BMI has once again come under increasing criticism as a measure of health of late. Many people feel it lacks credibility, is outdated and generally irrelevant. However, does it still hold some credibility or is it right for people to ignore, and if so what health markers should be used in it’s place? Let’s have a look…

BMI was first introduced by Adolphe Quetelet (it can also be referred to as the Quetelet Index of obesity). Your BMI score is calculated by taking your weight (in kilograms) and dividing it by your height squared (in metres). In simple terms, BMI is a way of comparing the weights of groups of people of different heights.

The problems with BMI come predominantly from the misunderstanding of its use. It was devised as a measure of obesity, not as a general health marker or even to define whether people were a healthy weight or not. It was devised to determine HOW obese someone was, not IF they were. Over the years however it became the gold standard tool used by doctors, researchers and even the media in determining a healthy weight.

By definition, it assesses body mass and if it was devised to measure obesity, then it’s fair to say that its assumption of body mass being predominantly fat was a fair one to begin with. As soon as you start using it on the general populations however, it becomes much less effective as a measurement tool. Even less so when using it to assess those who engage in regular physical activity resulting in increased muscle mass.

The decision to adopt BMI as a general health marker is one which has caused much confusion amongst the general public about what a healthy weight really is for them and as long as the press and health organisations keep BMI in the public eye it will come under increasing criticism and lose value.

Rather than relying on one dated and misunderstood formula, the public need to understand that assessing health can be a complex issue with many variables to consider Health is a multi-dimensional concept.

As outlined, BMI does have its place. However, other measurables which can be used to give an indication of health include the following:

How you feel – Do you feel healthy? Can you exercise without pain and carry out your daily tasks in comfort? Generally how you feel is a good indicator of health. Your body is very good at letting you know when something is amiss. It’s important to be honest with yourself though, you cant hide very long from poor health.

Lean body mass and fat mass measurement – unlike BMI an assessment of these factors tells you how many kg of fat and muscle you’re holding. It indicates the quality of your weight, not just the quantity.

Waist to height ratio – this is calculated by dividing your waist circumference by your height. A ratio of 0.5 or more signals greater intra-abdominal fat, an indicator for increased risk of cardiovascular disease.

How you look in the mirror – we’re not fans of defining health by ‘looks’ (for the record, a six-pack does not equal healthy) but if you’re happy with what you see in the mirror and you feel healthy then that’s a sign you’re healthy too, not just physically but emotionally. Being happy with who you are and not conforming to what the media dictates is a strong asset to have in a world obsessed with unobtainable perfection.

Resting heart rate – generally speaking, the lower the heart rate the healthier you are. Lower than 70 beats per minute (bpm) is a sign you’re healthy and probably exercise regularly. Over 80 bpm is a sign you should probably exercise more. Exercise strengthens the heart after all.

Using a combination of the above to self-assess is a good way of keeping an eye on your health. However, consulting a doctor if you are worried about your health is a must. Just make sure they’re not solely using BMI to decide how healthy you are.

Edit & Update:

Following a recent discussion on my personal facebook page, Marilia Coutinhomade the following comment regarding BMI at a much higher level than just the individual:

"1. BMI is an extremely important nutritional epidemiology indicator. It is used by the WHO to map world hunger. Countries with over 20% of "thin adults" (adults with a BMI < 18) are considered as being under chronic hunger. Until a few years ago, India used to have 49% adults with a BMI < 18. Nigeria had 23%. Today, as the obesity epidemics is growing into the major killer in the world, claiming almost 60% of morbidity and mortality (since urbanization increased in recent years), the BMI again comes to the rescue to map the obesity crisis. So, no, the BMI is not irrelevant at all"

More here: https://storify.com/mariliacoutinho/obesity-and-the-who

You can follow Marilia on her Facebook page here: www.facebook.com/marilia.coutinho.pro


David Stache
Nutritionist and Co-Founder of Nourish