The History of BMI

The history of BMI starts in the 1800s with Adolphe Quetelet, a Belgian mathematician, astronomer, and statistician. He developed what later became known as the Quetelet Index: weight divided by height squared. The term “body mass index” came much later, but Quetelet’s formula became the foundation for the BMI score still used today.

BMI is now commonly used in public health, research, and adult weight category screening. It can help group adults into categories such as underweight, healthy weight, overweight, and obesity.

But BMI was not originally designed as a personal health diagnosis tool. It remains useful, but limited, because it does not directly measure body fat, muscle mass, waist size, bone density, fitness level, or overall health.

BMI was originally developed from the Quetelet Index, created by Belgian statistician Adolphe Quetelet in the 1800s. The formula compares weight with height squared. Today, BMI is used as a quick screening tool for adult weight categories, but it does not diagnose health or directly measure body fat.

What Is BMI?

BMI stands for body mass index. It is a number calculated from a person’s weight and height.

The basic BMI equation is:

BMI is used to estimate whether an adult’s weight falls into a general category. BMI is a measure of weight relative to height and a quick, low-cost screening measure for underweight, overweight, or obesity. BMI should be considered with other factors for individuals, such as blood pressure, cholesterol levels, and physical examination.

You can calculate your BMI online, then compare the result with the adult BMI chart.

Who Invented BMI?

BMI traces back to Adolphe Quetelet, a Belgian mathematician, astronomer, statistician, and social scientist who lived from 1796 to 1874. He developed the weight-to-height-squared formula in the 19th century while studying human body measurements across populations.

The formula was first known as the Quetelet Index, not BMI. A historical review in Nephrology Dialysis Transplantation explains that Quetelet described the index in 1832 as weight in kilograms divided by height in meters squared.

That means Quetelet did not invent “BMI” as we know it today. He created the mathematical index that later became BMI.

This is an important difference.

Quetelet was not designing a modern personal health calculator. His work was part of population measurement and statistical research. The modern use of BMI in medicine and public health came later.

What Was the Quetelet Index?

The Quetelet Index was the original name for the formula now widely known as BMI.

The formula was:

Weight ÷ height²

Quetelet was interested in patterns across groups of people. He studied averages and variation in human measurements. His goal was not to diagnose individual health conditions.

The Quetelet Index became useful because it gave researchers a simple way to compare body weight across people of different heights. Weight alone is not very helpful because taller people naturally tend to weigh more than shorter people. By adjusting weight for height squared, the index created a more consistent comparison.

For example:

This is the basic idea behind the BMI equation: weight should be interpreted in relation to height.

Why Was BMI Created?

BMI was not created as a fitness score or a full health test.

It was created from a statistical interest in human body size. Quetelet wanted to understand average physical patterns across groups. Later, researchers found that the same formula could help compare weight status in population health studies.

BMI became useful because it was:

• Easy to calculate
• Based on simple measurements
• Low-cost
• Useful for comparing large groups
• Practical for public health tracking
• Easier to standardize than many body composition methods

The CDC describes BMI as a valuable population health measure used worldwide. It also describes BMI as a screening measure for underweight, overweight, or obesity.

That population-level use is one of the main reasons BMI became so common.

How Did the Quetelet Index Become BMI?

The Quetelet Index became known as body mass index much later.

The modern term “body mass index” is commonly linked to researcher Ancel Keys and colleagues, who used the term in a 1972 paper studying indices of relative weight and obesity. Historical literature notes that the Quetelet formula became the strongest practical index for weight relative to height, especially as epidemiology grew after World War II.

The formula did not change much. What changed was how widely it was used and what people called it.

Why Did BMI Become So Widely Used?

BMI became widely used because it solved a practical problem.

Public health researchers needed a simple way to estimate weight categories across large numbers of people. More detailed body composition tests were harder, slower, and more expensive. BMI only required height and weight, so it was easier to use in surveys, clinics, research, and population tracking.

This does not mean BMI is perfect. It means BMI is practical.

BMI is especially useful when looking at broad trends, such as:

• Underweight rates across a population
• Overweight rates across age groups
• Obesity prevalence over time
• Public health patterns by region
• Large-scale research comparisons

The WHO uses BMI-based indicators for adult underweight, overweight, and obesity prevalence in global health data. For adults, WHO tracks indicators such as BMI below 18.5, BMI 25 or higher, and BMI 30 or higher.

That kind of population tracking is where BMI has the strongest use.

How Is BMI Used Today?

Today, BMI is used in several ways.

1. Adult Weight Category Screening

BMI is commonly used to estimate whether an adult falls into a standard weight category.

The CDC lists adult BMI categories as:

The CDC also lists obesity classes: Class 1 obesity from 30 to less than 35, Class 2 from 35 to less than 40, and Class 3 at 40 or greater.

2. Public Health Research

BMI is used to study weight patterns across populations. It helps researchers compare trends by time, place, age group, and other factors.

3. Health Risk Screening

A BMI result may help identify people who could benefit from further health assessment. But it should not be used alone to diagnose a condition.

4. Clinical Conversations

Some healthcare professionals use BMI as one part of a broader conversation about weight, health risks, waist size, lab tests, lifestyle, and medical history.

Why BMI Is Still Used Despite Its Limits

BMI is still used because it is simple, consistent, and useful for broad screening.

It does not require expensive equipment. It does not need a lab test. It can be calculated quickly from weight and height. This makes BMI practical for large health surveys, research, and basic adult screening.

But BMI should be used carefully.

A better way to understand BMI is:

BMI is useful for screening, but not enough for diagnosis.

This is why modern health discussions often pair BMI with other measurements, such as:

• Waist circumference
• Waist-to-height ratio
• Blood pressure
• Blood sugar
• Cholesterol levels
• Physical activity
• Medical history
• Body composition measurements

The WHO describes BMI as a surrogate marker of fatness and notes that additional measurements, such as waist circumference, can help in obesity assessment.

So BMI still has value, but it works best when used with context.

Is BMI Outdated?

BMI is old, but that does not automatically make it useless.

What should BMI be used for?

BMI is still useful for:

• Basic adult weight category screening
• Population health research
• Tracking broad weight trends
• Starting health conversations

BMI is not enough for:

• Diagnosing health
• Measuring body fat directly
• Understanding muscle mass
• Judging fitness
• Measuring waist fat
• Explaining medical risk by itself

So, BMI should not be treated as the full picture. It should be treated as one simple measurement among many.

What to Remember About the History of BMI

The history of BMI shows why the number is both useful and limited.

BMI began as the Quetelet Index, a statistical formula developed by Adolphe Quetelet in the 1800s. It later became known as body mass index and became common in public health, research, and adult weight category screening.

Its strength is simplicity. Its weakness is also simplicity.

BMI can tell you how your weight compares with your height. It cannot tell you everything about your body, your health, or your future risk.

To use BMI well, calculate your number, compare it with BMI categories chart, then look at the broader picture. You can start with our free BMI calculator, then read about BMI limitations before making personal health decisions.

FAQs

Who invented BMI?

BMI traces back to Adolphe Quetelet, a Belgian mathematician, astronomer, and statistician. He developed the weight divided by height squared formula in the 1800s. At the time, it was known as the Quetelet Index. The modern term “body mass index” came later.

What was BMI originally called?

BMI was originally known as the Quetelet Index. It was named after Adolphe Quetelet, who described the formula in the 19th century. The formula compared weight with height squared, which is still the foundation of the BMI equation used today.

Was BMI created for doctors?

BMI was not originally created as a personal medical diagnosis tool. It came from statistical research into human body measurements and population patterns. Today, it is used in public health and health screening, but it should still be read with other health factors.

When did BMI become widely used?

BMI became more widely used in the 20th century, especially as researchers studied weight, obesity, and health risks across populations. The modern term “body mass index” became more common after research in the 1970s helped support its use as a practical weight-height index.

Why is BMI still used today?

BMI is still used because it is quick, low-cost, and easy to calculate from height and weight. It is useful for adult weight category screening and population health research. However, BMI does not directly measure body fat or diagnose health conditions.

Is BMI the same as the Quetelet Index?

The Quetelet Index is the original formula that later became known as BMI. Both use weight divided by height squared. The main difference is historical naming. “Quetelet Index” refers to the older name, while “body mass index” is the modern term.

What is the biggest limitation of BMI?

The biggest limitation of BMI is that it does not directly measure body fat or body composition. It cannot show muscle mass, waist size, bone density, fat distribution, fitness level, or overall health. This is why BMI should be used as a screening tool, not a diagnosis.

Disclaimer
This content is for educational use only. It does not replace medical advice, diagnosis, or treatment. BMI is a screening tool and does not directly measure body fat, muscle mass, waist size, or overall health. Speak with a qualified healthcare professional if you have concerns about your weight, BMI, or health.