Saturday, July 13, 2019

BMI: Biomarker for Longevity and Health

Photo by St. Murse
Body Mass Index, also called BMI, appears to be a simple tool for determining a healthy ratio between height and weight.

Not so.

Most people will agree to the truism that a person should not be too underweight or too overweight.

People should be just the right weight.

This post is part of a series on 18 biomarkers.

Note: The function of this post is only to raise awareness. It is not offering medical advice. If you have concerns about your BMI, please see a licensed medical professional. 

The BMI categories as published by the CDC are as follows:

Underweight = <18.5
Normal weight = 18.5 - 24.9
Overweight = 25 - 29.9
Obesity = BMI of 30 or greater
But the borders between these four categories are hotly debated as is the more general idea of "ideal weight."

Public discourse on body image, body shaming, lookism, and other related topics make this an intense topic.

This post discusses a JAMA report that suggests muscle mass as a better biomarker than the focus on body fat central to the BMI test.

Health Nucleas makes the argument that body composition (bone density, muscle mass, fat, etc.) should be measured, which is a little more complicated to accomplish. However, it's more informative.

I am not seeking to judge anyone or dictate a course of action.

For this reasons of controversy and complexity of methods of measurement, I have procrastinating writing about this particular biomarker as part of this series on 18 biomarkers of health and longevity.

According to this BMI Calculator, hosted by NIH, my own BMI has varied over the years of physical (and legal) adulthood from a BMI of 18.6 (point one away from Underweight) to a BMI of 25.4 (point six away from Overweight). 

Why is BMI a Biomarker of Longevity and Health? 

WebMD correlates obesity (BMI of 30+) with increased risk of heart disease, stroke, high blood pressure, high cholesterol, diabetes, gallbladder disease & gallstones, osteoarthritis, gout, and breathing problems such as sleep apnea and asthma.

The Centers for Disease Control includes all the above disease and conditions as part of the risks of obesity and also adds low quality of life, mental illness (depression, anxiety, etc.) as well as pain that makes body functioning difficult.

Measurement Tools

I have used a tape measure and a scale primarily; however, I have had skin calipers tests (aka skinfold  measurements or pinch test) used by my GP, by a university research team, and by a fitness trainer at the YMCA.

I have also had a DEXA scan (for bone density and ratios of muscle, fat, and bones) at Wichita State University as part of a battery of tests done for research participants 50 plus.

Photo by Mecklenburg County 
If you want to dive deeper into the range of BMI measurement tools available, this article briefly describes 7 different methods for assessing BMI. But not being an elite athlete or a person with heart disease, pursuing more methods of measurement seems like overkill.

I tend to use a bathroom scale, a tape measure, and the very informal and problematic method of "how my clothes fit." As an adult, I have gone down to a size 2 and up to a size 12. That's a pretty big range. The ideal is probably somewhere in the middle of those dress sizes. My height is just a little below 60 inches, unless I've done a lot of yoga recently to lengthen my spine.

(Caveat: I have often wondered, are clothing manufacturers making these sizes bigger to assuage the egos of Americans with expanding waistlines. That's another topic for another day.)

Be Well! 

However you measure, assess, and respond to the BMI biomarker, I wish you all the best in the pursuit of a long health span.


Biomarkers (18) for Longevity and Health

Weight-Hip Ratio: Biomarker of Health 

Daily or Weekly Weigh Ins? 

Goodbye Size 4


  1. This is fascinating, I am going to check my hip/waist ratio today. A couple years ago my doctor said my BMI is in the healthy range but I want to know more.

    1. It's interesting, but I am never totally sure what my ideal weight is. With BMI, I have to balance three things: my tendency of being obsessed about one thing or another, my need to be physically healthy, and my need to reduce my anxiety (about everything). Hugs and high fives to you, Terra!

  2. I'm always interested in longevity studies. Karen, you probably already heard about this, but about a month ago, I read that we need not push ourselves into walking 10,000 steps per day; instead, a goal of 4,000 steps is supposed to be the "magic number" to boost our health. That's a big difference. So far, I've been able to maintain the 4,000/day easily. Thanks for sharing such valuable info!

    1. Oh, I hadn't heard about the drop to 4,000/day. I'll have to look into that. Thanks, Pam.

  3. Very interesting. I knew what it was but not how it affected me per say. Thanks! (Rena)

    1. Thanks for the comment. There are a lot of research studies that I didn't discuss. There is so much that after two years of wondering how to cover several aspects of BMI, I decided to just skim the surface. It's interesting to see the proliferation of lab tests and studies about longevity. Have a great day.

  4. Healthy and Happy is my motto. Yes a BMI in the healthy zone is important but so is enjoying life. When I see a skinny person taking the skin off chicken wings let's say at a party I think first, why are they even eating chicken wings and second. that is not a happy individual and do not engage!

    1. Haralee: I like how you seek out happy people. I agree that one's attitude about food can often (but not always) be generalized, mainly because I can assess that in my own behavior / attitudes. If I'm happier, then I am less prone to be ritualistic about food. Thanks for stopping by the blog.