Girl working Out. Image: Health Magazine |
‘BMI is a person’s
weight in kilograms (kg) divided by his or her height in meters squared.’
This is one way to define it. Simple, huh? But don’t be
fooled. This seemingly simple definition is anything but. However, this isn’t
the time to jump the gun. So let me layer on the science of it.
BMI can also be calculated using other variables like pounds (instead
of kilogram) and with some calculators, it can be computed using feet and
inches instead of meters. The main components are weight and height. For the
purposes of this article, I will use kilogram to meters (or feet and inches)
for my measurements.
Let us get into it, shall we?
For a little over a hundred years, BMI has been used as the
standard of body measurement since Adolphe Quetelet, the
Belgian Mathematician, Astronomer and Statistician, developed the unit of
measurement. It seeks to measure whether a person is underweight, normal,
overweight or obese. Right now, the formula for calculating BMI is;
BMI = weight (kg) /
height (m2)
And generally, it is accepted that:
- A
BMI of 18.49 or below means a person is underweight;
- A
BMI of 18.5 to 24.99 means they are of normal weight;
- A
BMI of 25 to 29.99 means they are overweight;
- A
BMI of 30 or more means they are obese.
Until sometime last year, I accepted this measurement as
truth. I studied Biochemistry and I remember thoroughly enjoying the nutrition
classes because we dealt with things like BMI. I was especially happy about it
after I learned how to help malnourished babies get back to ‘normal’ weight. Those were the aspects of Biochemistry that made me love the course.
But recently, I had a run in with a loud-mouthed doctor when
I went to the hospital with my mum. She had suffered a heart attack. The doctor
stabilized her and after she had taken the drugs he gave her, she stood up and
went into the restroom. As soon as my mum was out of earshot and we were alone,
the doctor said something to the tune of, ‘if
you don’t want to suffer what your mother is suffering, you need to lose weight
quickly. Can’t you see that you are too fat?!’ (And yes…that was almost
verbatim). At first, I feigned laughter because he was a much older man and I
was worried about my mum. And then I wondered why he was making the comparison
because my mum is way slimmer than I am.
He persisted.
‘Climb the scale there.
I am sure your BMI will confirm what I am telling you. You are too overweight!’
This time, I didn’t laugh. And because I am not one to suffer a fool gladly, I made
sure I spoke pointedly at him so that he would get the message. ‘I am not your patient. Your job here is to
get my mum better; nothing more. Can you KINDLY focus on that?’
I am sure he hadn’t been spoken to like that in a while. He
kept quiet and waited for my mum to return. When he was done with his duties,
my mum and I left. It wasn’t until later that I heard he told my mum I was a
rude child. It gave me so much pleasure to have put him in his place. But… I
digress.
That day, I was so mad at the doctor. I saw what he did for
exactly what it was; fat shaming. The man didn’t really care about my health.
He didn’t have my medical history nor had he engaged me in a conversation to
find out about my lifestyle. All he saw was a fat girl that he thought he could
talk to in whatever way he felt he could. I wished I hadn’t been so
‘respectful’ of him and had given him a proper tongue lashing. And the more I
thought about it, the angrier I became.
But then, the anger passed. I looked at myself and admitted
what I already knew; I am fat. My BMI says I am obese.
But the question I asked myself after reaccepting
this fact was…am I healthy?
This question prompted another. ‘If BMI used just weight and height to classify people into normal
(which is translated to mean ‘healthy’) and obese (which is translated to mean
‘unhealthy’), could the unit of measurement be more about aesthetics than it
was about health?’
I decided to pursue the thought.
With almost 8 billion people in the world ranging from the
shortest person – Chandra
Bahadur Dangi who is just 54.64 cm – to Robert Wadlow who is
said to have been the tallest person in the world (standing at 8 ft 11.1 in),
there couldn’t possibly be a ‘normal’ height for people. This also meant that
there couldn’t possibly be a ‘normal’ weight for people. As I processed these
thoughts, I wondered: if you can’t have a normal height or weight, how can we
have a ‘normal’ BMI? Because, what may be normal to a 5’9 man weighing 70kg may
be underweight for a 7’1 person of the same weight, and overweight for a 5’4
woman of the same weight. So…if there was no constant in all this, how could
the BMI be accepted as the appropriate unit of measuring 'normal' health?
To process this thought further, I started doing some basic
mathematics in my head. It was too stressful for me, so I found a BMI
calculator that used the kilogram to feet and inches ratio. I started to
calculate BMIs for a range of people if one variable was kept constant. Here is
what I found.
Height (Feet/Inches)
|
Weight in Kilograms
|
|||||
26
|
50
|
100
|
150
|
200
|
635
|
|
1'7"
|
111.63
|
214.58
|
429.36
|
644.05
|
858.73
|
2726.46
|
4'8"
|
12.9
|
24.71
|
49.43
|
74.14
|
98.85
|
313.86
|
4'10"
|
12
|
23.04
|
46.08
|
69.11
|
92.15
|
292.58
|
4'11"
|
11.6
|
22.26
|
44.53
|
66.79
|
89.06
|
282.75
|
5'
|
11.2
|
21.53
|
43.06
|
64.58
|
86.11
|
273.4
|
5'1"
|
10.8
|
20.83
|
41.66
|
62.48
|
83.31
|
264.51
|
5'2"
|
10.5
|
20.16
|
40.32
|
60.48
|
80.65
|
256.05
|
5'3"
|
10.2
|
19.53
|
39.05
|
58.58
|
78.11
|
247.98
|
5'4"
|
9.8
|
18.82
|
37.84
|
56.76
|
75.68
|
240.3
|
5'5"
|
9.5
|
18.34
|
36.69
|
55.03
|
73.37
|
232.96
|
5'6"
|
9.3
|
17.79
|
35.58
|
53.37
|
71.17
|
225.95
|
5'7"
|
9
|
17.26
|
34.53
|
51.79
|
69.06
|
219.26
|
5'8"
|
8.7
|
16.76
|
33.52
|
50.28
|
67.04
|
212.86
|
5'9"
|
8.5
|
16.28
|
32.56
|
48.83
|
65.11
|
206.73
|
6'
|
7.8
|
14.95
|
29.9
|
44.85
|
59.8
|
189.86
|
6'1"
|
7.56
|
14.54
|
29.09
|
43.63
|
58.17
|
184.7
|
6'2"
|
7.36
|
14.15
|
28.31
|
42.46
|
56.61
|
179.74
|
6'3"
|
7.16
|
13.78
|
27.56
|
41.33
|
55.11
|
174.98
|
6'4"
|
6.98
|
13.42
|
26.84
|
40.25
|
53.67
|
170.4
|
6'5"
|
6.8
|
13.07
|
26.14
|
39.21
|
52.29
|
166.01
|
6'6"
|
6.62
|
12.74
|
25.48
|
38.22
|
50.95
|
161.78
|
6'7"
|
6.46
|
12.42
|
24.48
|
37.25
|
49.67
|
157.71
|
6'8"
|
6.3
|
12.11
|
24.22
|
36.33
|
48.44
|
153.79
|
6'9"
|
6.14
|
11.81
|
23.62
|
35.44
|
47.25
|
150.02
|
6'10"
|
5.99
|
11.53
|
23.05
|
34.58
|
46.1
|
146.38
|
6'11"
|
5.85
|
11.25
|
22.5
|
33.75
|
45
|
142.87
|
7'
|
5.71
|
10.98
|
21.97
|
32.95
|
43.93
|
139.49
|
7'1"
|
5.58
|
10.73
|
21.45
|
32.18
|
42.91
|
136.23
|
7'2"
|
5.45
|
10.48
|
20.96
|
31.44
|
41.91
|
133.08
|
7'3"
|
5.32
|
10.24
|
20.48
|
30.72
|
40.96
|
130.04
|
7'4"
|
5.2
|
10.01
|
20.02
|
30.02
|
40.03
|
127.1
|
7'5"
|
5.09
|
9.78
|
19.57
|
29.35
|
39.14
|
124.26
|
8'11"
|
3.52
|
6.11
|
13.54
|
20.31
|
27.08
|
85.97
|
Chart
showing varying BMIs where;
Yellow =
Underweight
Blue =
Normal
Grey =
Overweight
Red = Obese
I used the RKM
BMI Calculator to arrive at my figures. The first thing I noticed as I
calculated these BMIs was that I got a prompt only when the calculated index was termed overweight. It was
surprising because, if the worry was about determining health, it should have
prompted me when all the figures that fell into the underweight categories were
calculated. In fact, all the BMIs above 150 showed an ‘impossible’ prompt;
meaning people couldn’t - or maybe shouldn't - have those indices.
This seemed to be buttressing my view; BMI is designed to keep people skinny more than it is to keep them healthy. From my calculations, you can see that the ‘best’ weight seems to be between 50 and 100kg. Anything more than that and we have the obesity label slapped on an individual.
But let us think about this a little more.
Lebron James, the American and Los Angeles Lakers Basketballer,
is approximately 6 feet 7 inches tall and weighs 113kg. His BMI is 28.06. His
BMI says that he is overweight; and thus, unhealthy. Serena Williams – the
world class tennis player – is 5 feet 7 inches and weighs 70kg. Her BMI – 24.17
– shows her to be of ‘normal’ weight but you would never believe that with how
much people tear into her for supposedly being ‘big’ and ‘towering’. Remember
that nonsense by Maria
Sharapova? The sheer idiocy! Moving on, let us look at Simone Biles, the
American gymnast. Her 4 feet 7 inches frame weights 47kg. This brings her BMI
to the upper limit of ‘normal’. And finally, Shaq O’neil – the former
Basketballer – who weighs 147kg and stands at approximately 7 feet 1 inches has
a BMI of 31.54. This means that he is obese.
Here is why all these make no sense.
BMI doesn’t take into account a person’s food choices,
lifestyle, exercise or even whether their weight is fat or muscle mass. In
fact, it doesn’t take gender differences into account, or physiological changes like those
seen with pregnancy. It focuses on two variables that are too simplistic to be
effective. Which is why, looking at just their heights and weights, it is
simple to say Lebron is overweight and Shaq, obese. It is also easy to conclude
that based on these descriptions, they are unhealthy. Is that so however? The
answer is no.
Lebron is an athlete with a strict exercise and feeding
habit. And it is clear even just by looking at him that he is made up of more
muscle than he is of fat. Serena may look big but at 70kg, she is pretty
average. Simone doesn’t in anyway look like she weights 47kg. And while Shaq is
supposedly obese, his frame is fitting for his weight. Therefore, BMI in their
cases is a redundant measure of their state of health.
This made me do more research to see if other people
considered BMI to be a flawed unit of measurement for people’s health. And the
more I searched, the more it seemed that the science community was agreeing
with me; or better put, I was agreeing
with the science community.
It was while basking in the fact that I was right that I
stumbled onto something surprising. There is a new alternative to BMI! It is
called the Relative Fat Mass Index or RFM.
Orison Woolcot, a lead researcher at the Cedars-Sinai Medical
Center in California describe it thus. With RFM, ‘it's
the distance around your waist in relation to your height that counts, rather
than your weight. The researchers say that gives a better idea of whether
someone's body fat is at a healthy level or not.’
I was intrigued. So I learned more about this new method.
It would seem that to calculate what your RFM is, you would
be expected to measure your height and waist circumference, and then use this
formula below to calculate it:
64 − (20 × height/waist
circumference) + (12 × sex), where sex = 0 for men and 1 for women.
This means that the formula dis-aggregated is thus;
MEN: 64 – (20 x height/waist circumference) = RFM
WOMEN: 76 – (20 x height/waist circumference) = RFM
On a side note, I don’t know why there is a difference in the formulas
for men and women. I will have to find out and update.
So what makes RFM a better alternative? I think the fact that
RFM presented near similar results to the dual energy
X-ray absorptiometry (DXA) body scan – defined as the gold standard for
measuring body tissue, bone, muscle and fat – is something to look into. In
simpler terms, RFM presented similar results to the ones produced by a machine
and, I am not saying machines cannot be
wrong, but… it presents a pretty convincing argument.
There are other methods that have been developed to
accurately measure a person’s health based on the fat tissues in their body,
but BMI still remains the most commonly used method. Why are these other
methods – shown to be way better at telling the health of a person than the BMI
– not catching on in general practice?
I think the answer goes back to the doctor’s reaction to my
weight.
BMI is not designed to give people an overview of their
health. If it was, it would put as much emphasis on underweight people as it did overweight and obese people. Again,
look at what happened with the calculator I used. It prompted me every time the result was ‘obese’ but
never when the result was severely underweight. Both extremes present potential
health problems for people, but only one got the stick.
At this point, the answer is pretty clear to me; BMI is
designed to keep the populace thin more than it is to keep it healthy.
To give this more credence, it is important to note that for
centuries, the global beauty standard for women was skinny or thin; with few
exceptions. Women did all they could to maintain weights that were nearly
impossible to keep without extreme exercise, starvation or severe health risks.
It is why many people initially didn’t call out anorexia, bulimia, excessive
smoking and even starvation because it achieved the results that were accepted;
skinny women. It is also why when a skinny person eats a lot of food, nothing
is said to them. In fact, they are praised for being able to put so much away
and ‘maintain their figure’. But God bless that a fat person eats...
However, with the advent of the body positivity movement,
things have begun to change. There is a conscious decision to show that health is
not just about weight and height, but also about the quality (and quantity) of
food eaten, whether a person is active or sedentary, how much exercise they are
doing, and what makes up the bulk of their weight; fat or muscle. Like most
social changes, it has been met with fierce rebuttal and in some cases, attacks.
But it is to be expected.
I believe that overall health is determined by way too many
factors to be allowed to rest on the shoulders of archaic methods of
measurement like the BMI. And fat doesn’t necessarily mean poor health…just as
being skinny doesn’t necessarily equate to good health. So it is time we
stopped using BMI to try to shame fat people into losing weight; it is a
failing ploy anyways.
I need to clarify that this is not a call for people to
disregard their weight as it affects their health. It is important to be
healthy and this entails living and eating right, exercising, having more
muscle mass than fat tissues and generally caring for your body.
So yes! The time to stop using BMI has come. And if one more
person tried to ‘worry about my health’ for me, without taking out time to find
out the parameters that determine said health, I am (literally) going to go
nuclear on them.
I kid. Or... do I?
PS: Here are some good BMI Calculators that incorporate other
health determinants that you may want to check out.
2.
NHS UK
No comments:
Post a Comment