What is a BMI index? | Exercise.com Learn: Your Fitness Business Resource

What is a BMI index?

Tyler Spraul is the director of UX and the head trainer for Exercise.com. He has his Bachelor of Science degree in pre-medicine and is an NSCA-certified strength and conditioning specialist. He is a former All-American soccer player and still coaches soccer today. In his free time, he enjoys reading, learning, and living the dad life. He has been featured in Shape, Healthline, HuffPost, Women's...

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UPDATED: Aug 25, 2020

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  • The BMI is a single number that is said to evaluate a person’s weight status relative to their height.
  • According to “accepted” guidelines, there are different ranges indicating health, overweight, and obese.
  • The story of the BMI starts in 1832 when Adolphe Quetelet started work on the “Quetelet Index.”

What exactly is BMI? How accurate is the Body Mass Index anyway? Well, check out the graphic below to find out for yourself!


Read on to learn more about BMI and then be sure to sign up for an Exercise.com PRO plan to get and keep your BMI on the right track!

Your BMI and You

We live in a weight-obsessed society. The Standard American Diet (SAD) has left this country with a slew of debilitating ailments for which there are no easy solutions.

One device that many people and doctors use to track fluctuations in body weight and their relationship to overall health is the Body Mass Index or BMI.

The BMI is a single number that is said to evaluate a person’s weight status relative to their height.

The simple formula for BMI is (weight [lbs] x 703) / (height squared [in inches squared]). This formula doesn’t take into account differences in weight/density between bone, muscle, fat, organs, or water stored in the body.

It’s just a big simple number that tried to boil down an extremely complicated issue into something easy to understand.

Unfortunately, it’s not that simple. BMI is NOT a diagnostic tool. It can be used as a guideline to track weight issues, but that is all.

According to “accepted” guidelines, there are different ranges indicating health, overweight, and obese.

  • Healthy individuals are said to reside within the 18.5 to 24.9 range
  • People with BMIs greater than 25 but less than 30 are labeled overweight
  • Those with BMIs over 30 are considered obese

The History of the Body Mass Index

The BMI has a long and colorful history of scientists and doctors trying to unravel the secret relationships between weight and health and diet and exercise and everything else that makes humans tick.

It kind of makes you wonder how humans ever got along before modern medical science came along to tell them what was wrong with them and what they were doing.

The story of the BMI starts in 1832 when Adolphe Quetelet started work on the “Quetelet Index.” Quetelet was searching for the medically/scientifically “normal” human.

Presumably, it was important to discern a baseline for a standard human so that abnormalities could be noted and medical/scientific research conducted.

The early 20th century saw the rise of insurance companies lead to the first-ever large-scale study of health as pertains to obesity and weight.

Apparently, when money starts to enter into the picture, everyone starts wanting to know more about what makes people sick, fat, and dead.

Insurance companies wanted to know and show the relationship between overweight people and early death (presumably so that they could start charging more money).

The early 1900s went on to reveal many other maladies associated with being overweight and obese. Among these were (and still are) diabetes, hypertension, and heart disease. Many of these have been linked to excess adipose tissue.

Jumping forward to 1972 we see Ancel Keys (father of the “Lipid Hypothesis”) publishing his “Indices of Relative Weight and Obesity.”

This tome purports to examine various height vs. weight indices in order to ascertain which formula did, indeed, reveal the most telling relationship between height, weight, obesity, and good health.

Keys puts forward the “Quetelet Index” as the best possible match, thereby signifying that medical science had advanced not at all in 140 years.

In the 1980s the BMI becomes the international standard by which obesity and height/weight issues are compared and judged.

The 1990s has the government launching healthy eating and exercising programs. This is when the BMI first becomes widely known.

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Population Numbers

Now that the BMI has become the yardstick by which all countries and peoples are judged for their height/weight health, it’s worth seeing how the US stacks up against the rest of the world.

An immense 33% of our ENTIRE population weighs in at more than 30 on the BMI scale. Mexico (our neighbor to the south) is fast behind us with 24.2% of people being obese.

No other countries on our list come anywhere near those numbers. Norway is down around 8.3% and Switzerland is even lower than that at 7.7%. Korea and Japan both have 3.2% obesity, which is not much at all.

In fact, the distribution numbers of “overweight” and “obese” for adults are pretty chilling. Nearly two-thirds of adults are overweight, while one-third of adults are obese – which means that in the US, pretty much everyone over 18 is overweight.

It’s not just adults either – more and more children are being recorded as overweight and obese. Ten percent of children ages two to five are obese.

That number doubles in the six to 11 age range, with 20% being obese. It more or less holds steady into young adulthood, however, with only 18% of adolescents (ages 12 to 19) being obese.

Taking Control

A number of different factors influence BMI. Heredity and genetics can make you taller or shorter or more likely to store fat or burn it up as fuel.

However, the food that you eat plays a major role in your BMI. The types of foods you eat and the effect that they have on insulin levels can also cause you to store food as fat.

However, buying higher quality foods and supplements can help you manage your BMI and keep your weight within healthy levels.

Exercise and activity levels can also influence BMI and have beneficial effects on insulin sensitivity and blood pressure.

Go PRO today to take advantage of our workout plans, exercises, and challenges to keep your BMI right where it needs to be!

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