What is the Body Mass Index and is it the best measure of obesity? - CrowdScience, BBC World Service
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- Опубликовано: 31 май 2024
- CrowdScience listener Maik wants to know what the Body Mass Index is and what his BMI score says about his body.
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Maik trains dogs for a living and wonders if, like different breeds of dog, we simply have different body types?
So, Marnie Chesterton comes up with some answers, talking to doctors about how the BMI is used and misused in clinical practice, and looks at some alternative methods for measuring our body composition. She also sits down with philosopher Kate Manne to discuss the realities of living in a fatphobic world.
We hear from Tonga in the South Pacific, where high BMI scores have labelled the country highly obese. But this is not necessarily how Tongans see themselves.
And Marnie finds out if the BMI will continue to be used across the world as an important health marker to say whether people are healthy, overweight or obese, or whether it is destined for the scrap heap of medical history.
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00:00 How to calculate BMI
01:20 Listener Maik wants to know what BMI can tell you about your health?
02:20 How the WHO uses BMI to classify weight
03:05 History of BMI and its inventor
04:15 What the BMI tell us and why excess fat can be bad for our health
06:40 What other kinds of health screening are there? Marnie enters the BodPod
11:35 What Tongans think about their weight and the BMI
16:04 How useful is the BMI?
17:20 BMI and access to health care
19:10 Weight stigma, or fatphobia, and the BMI's role
21:40 The BMI classifications were changed in the late 1990s
24:14 Should we stop using BMI?
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@14:00 In Tonga, and with many colonized countries, the issue is that they aren't eating their traditional native foods anymore. I have heard stories of native Alaskan ppl being sick on western foods going back to their native foods and after months to years they no longer have diabetes, high blood pressure, etc.
Yes... specifically I understand Australia (and NZ) have sent low cost meats of cuts that they don't eat to the Pacific islands. So that is a cause too.
the trouble is modern western foods are more delicious (salt, fat , sugar, msg etc) and cheaper to produce
I think the BMI is a fairly good guideline for most people. It’s not perfect of course but I don’t get some of the criticism. Come on, everyone knows if they are more the type „bodybuilder“ or „couch potato“. And your doctor can see it. Serena Williams knows she’s not overweight but very muscular.
I don’t like how the guy from Tonga sugarcoats Tonga‘s high obesity rate. There’s a difference between larger build and obesity. In Tonga 13% of the people aged 20-79 have diabetes type 2. I watched a documentary about Nauru and how the obesity rate of its population skyrocketed after industrialized countries ruined their environment and started to supply them with cheap ultra processed foods. We need to address this issues instead of sugarcoating obesity. If you want to help marginalized people you need to find out why they are obese instead of claiming that by addressing the issue you are being racist.
2:12 one of the biggest issues is this: ‘my neighbors can eat what they want’ and they are thin.
At minimum 50% of people, that are ‘normal’ BMI are significantly insulin resistant if not raging type 2.
We each have a ‘personal fat threshold’. Someone can have a BMI of 40 and less visceral or organ fat than someone with a 23 BMI. TOFI. Thin outside, fat inside.
But there is no health at every size. Too much adiposity even in safe subcutaneous fat, creates chronic inflammation.
So it’s the case in today’s world that many ‘normal’ BMI are as obese as the rest of us that can actually get obese.
I did reverse my morbid obesity. Noting fancy: tasty real food, intermittent fasting, falling in love with natural fat and salt. Not sexy, super effective.
But don’t chase weight loss. I was interested In health. When I found out I could eat steaks and broccoli lathered in butter, my success was assured:
Focus on transforming relationship with food, getting healthy, move better, sleep better, fast better. The weight loss follows 🥰🌞🥰
I agree. Focus on health and wellbeing, not weight loss.
I think waist-to-height and waist-to-hip ratios are better predictors of obesity risks. Clinical tests such as complete blood count, blood pressure, and other tests are more useful than bmi and the ratios mentioned above.
It's a "cheap and cheerful" measure. Body fat composition is not accessible to everybody at home. Too much fat, particularly visceral fat, compromises health. BMI is far from perfect, but it's a starting point for further investigation.
So at just over 6’ and 75kg I look skinny but have non alcoholic fatty liver disease. This despite running and some weights and feeling healthy at age 62. When In was slightly overweight according to BMI then the last time at 85kg it was less excercise and more biscuits, however I’ve been that with earlier in life with consistent work in the gym so it illustrates the points that you are making, that it’s a poor measure of my health.
Thank you so much, this was an excellent overview 👌🏻
As the video says: BMI is not and was never meant to be a measurement of health. Anyone who does that anyway, does not really know what he/she is doing. As is popular in computers: RTFM. That is always good advice.
I was 102 kilos and with health of my dietician I reach my normal BMI . It's important to understand that you should be educated by career how to combinate the food. There's no meaning to be slim and to eat harmful products . Or your goals are only to lose your weight.
I think it's another way not to take responsibility for our choices and actions. I especially dislike the argument that bodies come every shape size. Historically humans never had constant access to this amount of food. Preserving fat was a tool to survive famine, which occured regularly.
Now it's on us to say no to excess food, as our body is not smart enough to do so
We know that visceral fat is the real problem- too much increases the risk of a range of diseases. BMI is a rough but sometimes inaccurate screening tool for excess visceral fat. Not many people can afford an accurate but expensive,say, DEXA scan. That said, by the time one’s BMI is in the obese category, unless you’re a professional bodybuilder, you know you likely have too much visceral fat. No shaming here, just a medical condition to be addressed.
How about waist hip and waist height ratios?
This too is problematic as short waisted people’s waist measurement is closely related to their hip measurement, there’s only so much area you can squish your internal organs into….
People need to grow a spine. Admit it. You are fat. I am fat. Life is not all rainbows and unicorns.
Nice very helpful video i am from India
There had been so much fuss about BMI so much so that people become obsessed by it. But a low BMI is misleading. A regular consultation with one’s practitioner coupled with full bloodwork will help assess one’s health situation better. I for one has always had a low BMI only to find out my blood markers show otherwise; thin on the outside but “fat” on the inside. I find a regular check with my GP is more beneficial in catching underlying health issues early enough thankfully.
The word "diet" is now used to mean some (often faddy, drastic) short-term weight loss intervention that people either can't stick to at all, or cannot wait to revert back to their previous eating patterns - hence their high failure rate. If you adopt a healthy but satisfying eating pattern with a view to sticking with it FOR LIFE, you'll be able to keep the excess weight off once you've lost it. I believe the biggest enemy nowadays is ultra processed food, scientifically designed to encourage over-consumption of unhealthy chemical substances masquerading as food. It's really difficult to avoid consuming this stuff, it's ubiquitous and looks like the real thing (until you read the ingredient labels) but it's worth trying. "Garbage in, garbage out" doesn't just apply to computer programs.
FFS, if you have a BMI of 30, you need to lose weight! When I was slim, I was at 25 because I'm at the higher end of BMI... But now I'm at 30 and it's because I weigh over 100 kg which is not healthy!! I think the female presenter is in denial....
I think waist should be measured against the hips ratio. Legs and arms are healthly when they are big specially if it's mostly muscle mixed with fat.
0:23 Isn’t it weight divided by square meters of height?
May have been in metres for the original BMI tables, but "cm" are more used for metric measurements of height e.g. all online metric calculators ask for measures of height using "cm".
When it comes to doctors advising their patients to add or loose weight as a result of their BMI number (as they do unfortunately) it can be disastrous for someone who it doesnt apply to. People trust their doctors
Remember Arnold Schwarzenegger had a BMI of 31 during the peak of his bodybuilding career
My physician doesn't buy into BMI but has to record it to get payment from the insurance company
Oh yeah, 'cos _so many_ people are elite body builders.... BMI is a good indication for the vast majority of people.
Steroid use will allow you to put on more muscle than the average man. As stated in the video, muscle weighs more than fat.
BMI is a good indicator for most normal people. You can also just look in the mirror. If you have a big gut, you’re overweight.
Obesity is overfat, not overweight. Even the use of BMI as an indicator of survival has aggregated all ages when, if you plot BMI by age, what are 'healthy' BMI ranges varies. Slightly higher BMI predicts longer life in over 60s.
Which is a more significant problem: the stigma around being obese, or the obesity itself?
Some countries use WHR and that seems to make much more sense, I think Japan does. Belly fat is a real killer, fat on your thighs (for a woman) is not
WHtR (or WSR with S for "Stature") is cheap, simple, works with a simple sum. UK officially adopted it as a better measure than BMI nearly 2 years ago (but I don't know if it's widespread yet). Japanese, other researchers have shown that it works with varied ethnic groups and ages.
0:24 At least learn what to divide by what.
Muscle phobic for sure
You're fat in your pic lol
"you ate your way in, you can walk your way out" Bill Burr
BMI doesn't make any sense to me. It would do if it were mass / height cubed rather than squared.
Why? Because with the current definition, it is skewed in favour of short people. Here's a hypothetical situation to explain this: Consider two people, one is 1 metre tall and the other is 2 metres tall. Also, and this is a KEY POINT the two people are proportioned exactly the same - in other words, the tall one is a magnified version of the small one. Assume that the short one weighs 20 kg. So let's calculate their BMI's, which is the weight in kg divided by the height in metres, squared.
The BMI of the short guy is 20 / (1 x 1) = 20 kg / m2. (A supposedly very healthy value.)
To calculate the BMI of the tall guy, we need to work out his weight. Remember, he has exactly the same proportions as the short guy, so if he is twice as tall, he's also twice as wide (side to side) and twice as thick (front to back). So his 'volume' will be 2 x 2 x 2 that of the short guy and therefore his weight will be 20 x 2 x 2 x 2 = 160 kg. His BMI is therefore 160 / (2 x 2) = 40 kg / m2.
So the tall guy has a BMI twice that of the short guy despite the fact they are both identically proportioned. Why does simply being taller but identically proportioned lead to a higher BMI? An identically proportion person will have all the vital organs and fat etc. in the same proportions as the short guy - yet, the BMI says he's unhealthy.
It doesn't make sense.
You are wondering why the person that is 2x as tall but 8x the weight has a higher BMI? Seems kinda self-explanatory
@@swimmerboy172 Yes, that's what the maths tells us, but the point is, it doesn't make sense. Someone who is twice as tall SHOULD weigh 8 times as much otherwise his proportions are wrong: twice as much because he's twice as tall, twice as much again because he's twice as wide (from side to side) and twice as much yet again because he's twice as thick (from front to back). And 2 x 2 x 2 = 8. If he's not 8 times as heavy, his proportions are wrong.
Think in terms of a cube, 1 x 1 x 1 metres and assume it weighs 1 kilogram. It's BMI is 1/(1x1) = 1.
Now stack 8 of these cubes together to make a larger cube 2 x 2 x 2 metres. This is just a larger cube but apart from that its properties are identical. Everything is in the same proportion, so if it were somehow alive it would be just as healthy, but its BMI is 8/(2x2) = 2, ie. twice that of the single cube.
So the question is why is BMI measured as weight/height squared, rather than weight/height cubed?
Either whoever invented BMI is hopeless at maths or there's some factor that I (and most others) don't appreciate as to why it's the way it is.
What!? It makes perfect sense,if you are 2 m tall and 160 kg weight,you are not healthy obviously
@@zlinos139 Your missing the point. It's the RELATIVE figures that count. If it helps, rework the figures with lighter people, starting with the tall guy. Assume that the 2 metre tall guy weighs 80 kg. His BMI is 80 / (2 x 2) = 20, which is a healthy figure.
Now scale him down to 1 metre in height to get an identically proportioned short guy. The short guy will weigh 80 / 8 = 10 kg and his BMI will be 10 / (1 x 1) = 10, which is far too low. Why? He has the exact same proportions as the tall guy and his weight is in the same proportion, but the BMI calculation leads to absurd figures.
@@chrisengland5523 Are you saying that in your calculations a person weighs 10kg and you want me to take your comment seriously?
BMI is a very flawed measure of anything, there was a pastor in the church I go to, who once stood on the pulpit (he is pretty tall and lanky and middle aged, so no muscles or athletic body to say that the BMI calculation took his muscle mass as fat), and the BMI calculation stated that he was obese which is ridiculous. He was joking about it on the pulpit. Ever since then, I realized that the BMI measurement is not accurate at all, and should not be used in any medical institution to determine obesity.
1.9m is 6 foot 3.
Ugh Ansel Keyes, champion of cereals :p
BMI is not proper to identify the degree of health.
Useful at a large level to see changes within a population, or (with caveats) to compare countries. I agree that it doesn't tell us much about individual health.
I dont think that was ever its goal, as per the host.
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As far as I know, dieting has a high failure rate because, often, it is practised without the aid of a professional...
The vast majority of them haven't got a clue themselves. Failure is due to wrong eating patterns/no willpower and our hormones failing us.... The problem is: if the right eating habits are not taught at home from childhood, it it very hard to un-learn them in adult life... Also most people haven't got a clue what "healthy eating" actually means...
So you seem to agree with me on the fact that this episode send a wrong message about dieting.
Not just that. It is also a matter of self-knowledge. I have struggled with my weight for over 40 years. Nothing worked... until I accidently found a way of eating that made it possible to be **less** hungry. Willpower did and does the rest. As a result, I lost well over 60 kg and am keeping them off.
The wrong message this episode conveys is that because of its high rate of failure dieting is not a reliable method to control your weight. I'm there a more people who quit the gym rather than people who keep up exercising, however, working out is undisputably beneficial...
@@Pietro-th1yd I wholeheartedly agree. Just because people don't do A is a nonsensical reason to say that A doesn't work.
Been to over 10 funerals never have I had any one complement a dead body having a good physique