BMI vs BF%: where is the true under/overweight marker?
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svel713
Posts: 141 Member
I hear people complain that body fat percentage is the best way to measure health.
So lets take some woman I know that is about an 18.2 BMI but is 18.5% BF. She does 70% cardio, 30% bodyweight exercises mixed with actual weights.
If she gains to 101.5lbs, she is now slightly in the normal range but hits just over 20% BF and loses all ab definition.
(BF% that is athetic is 14-20% for a woman. Below is essential fat.)
If body fat is a better marker of health, can we really say she is underweight? Would she be an outlier?
(BF measured by body fat scale and taking measurements with 1% range, for reference.)
So lets take some woman I know that is about an 18.2 BMI but is 18.5% BF. She does 70% cardio, 30% bodyweight exercises mixed with actual weights.
If she gains to 101.5lbs, she is now slightly in the normal range but hits just over 20% BF and loses all ab definition.
(BF% that is athetic is 14-20% for a woman. Below is essential fat.)
If body fat is a better marker of health, can we really say she is underweight? Would she be an outlier?
(BF measured by body fat scale and taking measurements with 1% range, for reference.)
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Replies
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At that weight, she'd benefit from muscle and fat gain.5
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A body fat percentage of 20 is perfectly fine for a female. It tells you that this woman it fit and healthy. Having ad definition does not make you healthier, especially if you are underweight.12
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Lillymoo01 wrote: »A body fat percentage of 20 is perfectly fine for a female. It tells you that this woman it fit and healthy. Having ad definition does not make you healthier, especially if you are underweight.
^^This.
The guidelines on body fat for women actually say this: Top athletes: 15 to 20%, Fit women: 21 to 24%, Healthy/acceptable: 25 to 32%
Ab definition is not the be all and end all, especially if you are potentially sacrificing your hormonal health for the sake of it.10 -
BMI vs BF% is a matter of apple and oranges.
BMI is associated w/but not directly correlated w/BF%. It was developed originally as a part of a mathematical study in the 1830's simply to determine the relationship between a person's height and weight.
It was only later much later accepted by the medical community in the 1990's when it was "standardized" by WHO and later adopted by NIH as a "scientifically" justified measure of obesity and one's risk for associated health problems.
BF% is just that - - a measure of the amount of BF (as measured by weight) relative to one's total body weight. It is NOT a measure of health per se.
Actual BF measurements are seldom done for medical purposes; doctors perferring to rely on simpler indicators like BMI or height to weight ratios as indicators of obesity and risk of health issues.
Attention to actual BF% seems to be more important in the fitness and bodybuilding community as a way of measuring and ranking one's appearance and "fitness" as compared w/others rather than a way to assess one's health.
Someone (male or female) w/a BMI bet 18.5 and 24.9 is considered to be of "normal" expected weight and not at any special risk for health problems due to obesity.
On the other hand, man w/a BF% of 18-20% would be considered "normal" while a women with that BF% would be considered "athletic" in appearance. However, in neither case would the BF% be used an indicator of healthiness.
So, OP, the example you use to contrasting the use of BMI vs BF% for the purpose measuring health is spurious. Only BMI is used for that purpose and, even so, there are many critics of it's validity for that use.
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BMI vs BF% is a matter of apple and oranges.
BMI is associated w/but not directly correlated w/BF%. It was developed originally as a part of a mathematical study in the 1830's simply to determine the relationship between a person's height and weight.
It was only later much later accepted by the medical community in the 1990's when it was "standardized" by WHO and later adopted by NIH as a "scientifically" justified measure of obesity and one's risk for associated health problems.
BF% is just that - - a measure of the amount of BF (as measured by weight) relative to one's total body weight. It is NOT a measure of health per se.
Actual BF measurements are seldom done for medical purposes; doctors perferring to rely on simpler indicators like BMI or height to weight ratios as indicators of obesity and risk of health issues.
Attention to actual BF% seems to be more important in the fitness and bodybuilding community as a way of measuring and ranking one's appearance and "fitness" as compared w/others rather than a way to assess one's health.
Someone (male or female) w/a BMI bet 18.5 and 24.9 is considered to be of "normal" expected weight and not at any special risk for health problems due to obesity.
On the other hand, man w/a BF% of 18-20% would be considered "normal" while a women with that BF% would be considered "athletic" in appearance. However, in neither case would the BF% be used an indicator of healthiness.
So, OP, the example you use to contrasting the use of BMI vs BF% for the purpose measuring health is spurious. Only BMI is used for that purpose and, even so, there are many critics of it's validity for that use.
Well said.1 -
Do people really think that ab definition is a health marker?10
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Lillymoo01 wrote: »A body fat percentage of 20 is perfectly fine for a female. It tells you that this woman it fit and healthy. Having ad definition does not make you healthier, especially if you are underweight.
This. Ab definition means that you have good genes and are fairly lean. It doesn't mean that you're magically healthy.3 -
Lillymoo01 wrote: »A body fat percentage of 20 is perfectly fine for a female. It tells you that this woman it fit and healthy. Having ad definition does not make you healthier, especially if you are underweight.
It doesn't mean its the look that the person wants, though. When I've asked women I know what body they want, they point to the 15-17% body fat example on the below page:
https://www.google.com/amp/s/www.builtlean.com/2012/09/24/body-fat-percentage-men-women/amp/
So at least the women around me want to be there. They want to look like the instagram models and 20% is still too "fat" for that.
And also, body fat is used as a measure of health. We judge certain risks by waist size, which is used to measure BF%. Which is part of why I asked.0 -
just because people want it doesnt' mean that its healthy...think back to twiggy in the 60's - people wanted to look like her....
waist size is used it very squishy measures of body fat (i.e. taping and calibers) which can have up to a 10% (IIRC) differential range3 -
Lillymoo01 wrote: »A body fat percentage of 20 is perfectly fine for a female. It tells you that this woman it fit and healthy. Having ad definition does not make you healthier, especially if you are underweight.
It doesn't mean its the look that the person wants, though. When I've asked women I know what body they want, they point to the 15-17% body fat example on the below page:
https://www.google.com/amp/s/www.builtlean.com/2012/09/24/body-fat-percentage-men-women/amp/
So at least the women around me want to be there. They want to look like the instagram models and 20% is still too "fat" for that.
And also, body fat is used as a measure of health. We judge certain risks by waist size, which is used to measure BF%. Which is part of why I asked.
But even the Instagram models don't look like that most of the time...7 -
Lillymoo01 wrote: »A body fat percentage of 20 is perfectly fine for a female. It tells you that this woman it fit and healthy. Having ad definition does not make you healthier, especially if you are underweight.
It doesn't mean its the look that the person wants, though. When I've asked women I know what body they want, they point to the 15-17% body fat example on the below page:
https://www.google.com/amp/s/www.builtlean.com/2012/09/24/body-fat-percentage-men-women/amp/
So at least the women around me want to be there. They want to look like the instagram models and 20% is still too "fat" for that.
And also, body fat is used as a measure of health. We judge certain risks by waist size, which is used to measure BF%. Which is part of why I asked.
Just because someone wants to look like something doesn't mean that it's healthy to do so.
Look at anorexics and bonespo. Is that healthy, just because it's what they want to look like?
(Protip: If you say yes, get yourself to a therapist.)
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Both body fat and BMI are useful indicators for health. Body fat is a more direct indicator while BMI is a more a general one. Body fat's biggest issue, and the reason health care professionals (HCP) and researchers don't utilize it often, is that it isn't an easy number to obtain, especially accurately. This is the reason you don't hear many statistics that involve body fat. BMI on the other hand is simple to obtain. It allows HCPs to draw fairly useful inferences for most people. It is irresponsible however for a HCP to look at BMI only and not ask themselves how it applies to the particular individual they are caring for. For example, I personally have a BMI in the overweight category yet my body fat percentage is in the athletic category. I am not at risk for almost any of the things someone with an BMI in my range is usually at risk for. Even a novice HCP can figure out why that is if they have even a basic understanding of what BMI is.
Body fat percentage is another beast in and of itself. As I stated before, it's not a number easily determined with decent accuracy. If that wasn't the case and we could find an accurate body fat percentage as easily as we could find a BMI I believe that more research would be directed towards body fat and health. Even then there would still be some issues. An example is someone who has a normal range body fat percentage but has an elevated amount of abdominal body fat. They share many risk factors of someone who has higher than normal body fat percentage.
Finally, just because you have normal BMI or body fat percentage doesn't mean you are healthy. Healthy is a fairly ambiguous term with many different meaning to different people. From a purely medical perspective we might say healthy is the absence of disease. Well, people with normal body fat and BMI can still be diabetic, hypertensive, have cancer, etc. This is why it's always so important to have a HCP that can do more than look at your "numbers" to determine if you are "healthy". You have to look at the person as a whole, and interrupt how those numbers should be applied to that individual. In short, both body fat and BMI can be useful indicators but like almost everything else health, diet, and fitness related, cannot be looked at in a vacuum.8 -
Lillymoo01 wrote: »A body fat percentage of 20 is perfectly fine for a female. It tells you that this woman it fit and healthy. Having ad definition does not make you healthier, especially if you are underweight.
It doesn't mean its the look that the person wants, though. When I've asked women I know what body they want, they point to the 15-17% body fat example on the below page:
https://www.google.com/amp/s/www.builtlean.com/2012/09/24/body-fat-percentage-men-women/amp/
So at least the women around me want to be there. They want to look like the instagram models and 20% is still too "fat" for that.
And also, body fat is used as a measure of health. We judge certain risks by waist size, which is used to measure BF%. Which is part of why I asked.
But even the Instagram models don't look like that most of the time...
I'm considering people who know how to pose like them and still don't look like them.
Like how you have to flex your abs for pictures to figure out what you really look like compared to athletes.6 -
They know how to use Photoshop and an air brush?
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I don’t get the question. People can be healthy at a wide range of weights and body fat percentages, the further you get in one direction doesn’t make you necessarily healthier. I do want to be below 20% body fat as a goal in life, but I don’t think I’m unhealthy or fat at 22%. I actually hate that way of thinking. And the idea that I would look like an Instagram model at any body fat percentage is near delusional.7
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