Everything You Need to Know About the Body Mass Index




A lot of us have been here before: you're at the doctor's office, and they'll say, "Your BMI is too high/low. You need to lose/gain weight." They're proceed to tell you a number and say you have to get that number up/down or you're more at-risk for heart disease. So, what is this BMI number, and how is it important? The Body Mass Index, or BMI, is a common tool used to measure health standards and obesity rates. Lately, however, it has fallen under scrutiny due to the belief that it doesn't accurately depict overall health. Let's dive in and see if the BMI has any validity.

How To Calculate BMI and What It Means


Equation:

703 x [ Weight (lbs.) / Height (inches squared) ]


Results: 

< 18: Underweight

18 - 24.9: Healthy

25 - 29.9: Overweight

30 - 39.9: Obese

> 40: Severely Obese

Example:
  • I weigh 180lbs and am 5'11". My equation looks like: 703 x [180 / (71^2)]. My BMI is 25.1, and I am classified as overweight. 
Please Note: 
  • The BMI scale categorizes individuals into ranges such as "overweight" or "obese," but it’s important to remember these are broad classifications. A more personalized health assessment is always a better way to understand your unique health profile.

What is BMI Used For?

BMI is used to measure obesity. While imperfect, it is an inexpensive and noninvasive way to determine an individual's overall health. There is a direct correlation between obesity and chronic heart problems (Powell-Wiley, 2021). Examples of this may include type 2 diabetes, hypertension (very high blood pressure) and sleep disorders. 

Why BMI Is Not Always Accurate

The BMI does not distinguish between muscle and fat. I have a body fat percentage under 15% and I am considered overweight by the BMI. Having a higher muscle mass means you have more mitochondria to burn calories, thus improving your metabolism and is good for overall health. What's important to consider, though, is that I have been training for over five years and have just hit the "unhealthy" mark. It is not common to have such a disproportionate amount of muscle than fat to be considered overweight. That said, it is not heart-healthy to carry around massive amounts of muscle, either (Paulauskaite, 2021). Weighing 300lbs is NOT good for your heart, regardless of if the weight is due to muscle or fat. 

Women carry more fat than men. Women tend to carry more fat in the gluteal-femoral region than men (Department of Human Biology at Maastricht University, 2001). This can be attributed to wider hips to assist with childbirth. Additionally, the difference between male and female athletes is astounding. Male athletes range between 6-13% body fat, and women range between 14-20% (Marsden 2024). For bodybuilders, it is recommended that males not drop below 3% and females not drop below 10% (Reason, n.d.). 

It doesn't consider age. As we get older, we tend to lose muscle and gain fat, resulting in a higher BMI even though overall health may not have been impacted. In fact, this fat gain is seen as a healthy sign, so much so that older individuals with a BMI under 23 are considered underweight (Lemond, 2023). 

Final Thoughts

While BMI may not be the perfect tool for assessing obesity or cardiovascular health, it can still provide a general overview of whether you’re in a healthy weight range. As a free and noninvasive screening tool, it can be useful for identifying potential health risks, but it shouldn’t be your only measure of well-being. If your BMI concerns you, it’s a good idea to consult a healthcare professional who can take a more comprehensive look at your overall health, including factors like body composition, metabolic health, and any underlying risks for chronic conditions. Remember, health is a complex picture, and BMI is just one piece of the puzzle.



References

Department of Human Biology at Maastrict University. (2001, November 4). Gender differences in fat metabolism. PubMed. Gender differences in fat metabolism - PubMed

Lemond, Angela. (2023, September 19). Is Body Mass Index (BMI) an Accurate Way to Measure Health? Everyday Health. Is Body Mass Index (BMI) an Accurate Way to Measure Health?

Paulauskaite, Egle. (2021, February 19). The fascinating truth about why big muscles aren't necessarily better. Aurum. Muscle mass: Why bigger muscles aren't necessarily better

Powell-Wiley, Tiffany M. (2021, April 22). Obesity and Cardiovascular Disease: A Scientific Statement from the American Heart Association. PubMed. Obesity and Cardiovascular Disease: A Scientific Statement From the American Heart Association - PubMed

Reason, Leigh. What Is a Good Body Fat Percentage for a Bodybuilder? Livestrong. What Is a Good Body Fat Percentage for a Bodybuilder? | livestrong

Typical Body Fat Percentages of Different Athletes. (2024, January 8). Marsden. Body Fat Percentages Of Different Athletes | Marsden Weighing

Comments

  1. Ryan I-BNovember 9, 2024 at 5:02 PM

    This was a very interesting dive into what exactly BMI means! It is something that is always tossed around without much context, so it was fun to learn more.

    ReplyDelete

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