Key Takeaways

What is body mass index (BMI) and why is it important?

Body mass index (BMI) is a measure of body fat based on weight and height. It helps determine if you are at a healthy weight, underweight, or overweight. BMI is important because it provides a baseline for assessing your overall health and risks for conditions such as heart disease, diabetes, and high blood pressure.

The language of fitness is now filled with measurements and calculations. We now know that there is more to getting fit and staying fit than simply counting calories and hitting the gym. Body mass index is one such measurement. While calculating things like cholesterol and blood sugar requires a visit to the doctor, and things like counting calories and carbs can get into some real math, body mass index is pretty easy to figure out. Body mass index is just a simple ratio of weight to height, but it can tell you quite a lot about your physical health and fitness.

Body mass index is also an important guide to how to begin other features of your fitness and diet plans. If you are counting calories, for example, your body mass index can help you determine how many calories you need to take in versus how many you need to burn in the form of exercise.

When working out a fitness, exercise, or diet plan we need to take stock of more than just our weight. Body mass index, or BMI, is a crucial measure of our fitness and general health. Body mass index gives you a baseline measurement to calculate other important factors in any weight loss or fitness regimen.

Just exactly what is body mass index? The terms seem to get tossed around as if we all know what they mean. Below we will explore the meaning of body mass index, what it is used for, and how to work with it toward your own fitness and health goals. 

What is Body Mass Index (BMI)?

Body mass index (BMI) is an estimate of your overall body fat based on your weight and height. While BMI is not a direct measurement, it does provide a solid working figure on which to base exercise and dieting plans. BMI can help determine if you are at a healthy weight or if you are overweight.

BMI can indicate whether or not you are carrying too much body fat or too little body fat. A low BMI can be a sign that you are underweight. BMI can also provide insight into your risk levels for other health problems like heart disease, high blood pressure, and diabetes. If your BMI is too low, you may be at risk for bone loss, anemia, and lower immunity.

It is important to bear in mind that BMI is an estimate. It is only an indicator, and if you suspect you may be at risk for health problems you should consult a physician for further examination. BMI may give an inaccurate indication of body fat in athletes, for example, because athletes tend to have so much muscle mass. BMI may also give an overestimate for elderly people who have lost muscle due to aging.

As a single measure, BMI is not the most accurate picture of your overall health. Some experts worry that too many healthy people are mislabeled as unhealthy by over-relying on BMI. Still, as a general gauge of health and fitness, BMI is a solid place to start. For most of us, we are just looking to get a general sense of how fit we are as we begin making adjustments to our diet and exercise. 

How to Calculate BMI Formulas

The implications of BMI differ for children, teens, and adults. The formula varies for each age group since teens, for example, will need a different BMI as they develop than older people.

Calculating your BMI is quite simple. BMI is calculated by dividing a person’s weight by the square of their height. For a person who is 5 ‘ 10’’ and 173 pounds, their BMI would come to 24/82. The Centers for Disease Control and Prevention (CDC) provide calculators that allow you to simply plug the numbers into an online source. They provide a calculator for children, teens, and adults.  These calculators also provide a sketch of your health status based on your BMI.

Again, while BMI is a good indicator of health and fitness, it is an estimate. If you are unsure of the status of your BMI, or if you have particular concerns, you should talk to your doctor about accurate tests that can measure things like cholesterol and blood pressure. 

Body Mass Index for Adults

In this case, the measure applies to people over the age of 20. The BMI applies the same for men and women since all your measuring is the total mass you carry. BMI does not give you a measurement of total fat or muscle, the value of which would differ between men and women.  

The BMI numbers fall into ranges as follows:

  • Below 18. 5 Underweight
  • 18.5-24.0 Normal
  • 25-29.9 Overweight
  • 30.0 and over Obese

Remember that these numbers are estimates. If your BMI gives you cause for concern, see your doctor get a more accurate read on your health. 

Children and BMI

BMI takes on a different meaning for people under the age of 20. While the BMI formula remains the same, the results are interpreted differently. The results have different implications for different ages and genders. As we grow, the amount of body fat we carry changes. Also, young girls and young boys require different levels of body fat for proper development. For example, girls usually acquire a higher amount of body fat than boys and they develop this earlier than boys.

The CDC provides charts for BMI for children that break things down according to percentiles. Each percentile is relative to other children in the same age range. A child who has a BMI in the 95th percentile, for instance, is considered obese since he or she has more body fat than 95 percent of other children of the same age. 

Breaking BMI down according to percentiles in children follows the chart below:

Percentile Weight Status

  • Below 5th Underweight
  • 5th-85th Normal
  • 85th-95th Overweight
  • 95th and over Obese

Use this chart as a gauge. The CDC provides age charts and other materials to help you interpret BMI results for children. 

What Does Your Result Mean?

The most recent surveys have found that over two in three adults are considered overweight. Of that group, one in three is considered obese. Roughly 17 percent of children and teens, ages 2- 19, are considered obese. We are living in a time of an obesity epidemic.

We gain weight when there is an imbalance of energy. We require a specific amount of energy to fuel basic physiological functions. This energy comes in the form of calories. A balance between energy in and energy used results in a healthy BMI. When we take in more calories than we need, these calories get stored in the form of fat. Too much fat and we tend toward a higher BMI.

This energy imbalance is the primary cause of weight gain and obesity. If your BMI falls within the normal range shown above, you are operating with a balanced energy load. The problem we are living with today is that too many of us take in the energy that far exceeds our needs and we reach an unhealthy BMI. It stands to reason that a high BMI is dangerous. Carrying around a high BMI puts stress on the body and leads to health problems.

Some recent studies have drawn the significance of BMI into question. Doctors are beginning to wonder if BMI really matters when it comes to measurements of health and fitness. In one study, researchers looked into BMI as a single metric of good health and found that it did not measure up well. Of those studied, almost half of the participants who had a high BMI actually had what is called a healthy cardiometabolic profile. This includes measures that evaluate cardiovascular health. This led them to conclude that BMI did not provide a reasonable picture of overall health.

In the same study, nearly one-third of those who had a healthy or normal BMI demonstrated signs of an unhealthy cardiometabolic profile. For these people to have relied on BMI alone as the measure of their health could have been dangerous. The final conclusion was that when placed against a medically determined cardiometabolic profile, BMI did not hold up as a reliable gauge of people’s health.

This said, doctors do not expect BMI to measure things like cardiovascular health, cholesterol levels, blood sugar, and blood pressure. It is certainly crucial to have these things properly evaluated by a doctor, and BMI is only intended to give you a basic starting point to begin thinking about your overall fitness. The conclusions of the above study do not discredit BMI. They merely point to the fact that we should have other, more specific factors professionally evaluated. 

Risks of a High BMI

Even given the questions that attend the accuracy and reliability of BMI as a gauge of our health, it remains a standard starting point to see if we are relatively overweight or underweight. In most cases, a high BMI is indicative of being overweight. As we know, carrying extra weight, especially in the case of obesity, is potentially dangerous. Since a high BMI naturally stresses our bodies, it makes sense that it is not a healthy thing to carry. High BMI can lead to a host of health problems. These health issues include:

  • heart disease
  • high blood pressure
  • liver disease
  • osteoarthritis
  • diabetes
  • stroke
  • gallstones
  • certain cancers, including breast, colon, and kidney cancers

While these health problems are associated with a BMI, recent studies have shown that it is specifically high body fat, and not BMI, that leads to health problems. The difference is that BMI does not necessarily correlate to body fat. As we saw above, athletes may show a high BMI as a result of a high ratio of muscle mass. If you do weight training for muscle development, you weigh more. It is that simple. But a BMI of this type is not linked to health issues.  

Wrapping Things Up

Body mass index offers a baseline metric for helping you determine your level of fitness and health. While it is an estimate and not a precise measurement, BMI does offer you a place to begin working out a plan for dieting or exercise.

Body mass index can show you where you fit in the range of healthy body weight. As a general rule, a high BMI is an indicator of being overweight or even obese. Since obesity presents a large problem in our society, BMI can offer you a good place to start in order to understand how you measure up. A high BMI would indicate that you need to lose weight. Low BMI shows that you are probably underweight. Just having this information can help you make healthy decisions.

Body mass index is an estimate. Keep this in mind if you take your own measurements and calculate your BMI. There are mitigating factors with respect to what BMI means for you. People with large amounts of muscle mass will show a high BMI but they are not overweight or obese. If you have concerns about what your BMI actually means it is best to consult your doctor to find out precisely how healthy you are.

In terms of what BMI means also changes when we apply this measurement to children. Since children are still growing and developing, the relative importance of BMI is measured in percentiles rather than static figures. Children require more or less body fat as they grow, and the relative health of BMI changes depending on what stage of development they have reached. Young girls and young boys also differ when it comes to the meaning of a BMI measurement.

But as a basic unit of measure for evaluating our health, body mass index works well. It gives you a gauge as to how much body fat you are carrying. From this, you can make reasonably informed decisions about your diet and exercise. For most of us, BMI works well as a way to get started on a program of health and fitness.

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At NF Sports, we're dedicated to supporting your fitness journey with high-quality, natural supplements made in an FDA-registered facility. Our content and product recommendations are for informational purposes only and are not intended as medical advice.

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1. What is Body Mass Index (BMI)?

Body Mass Index (BMI) is an estimate of body fat based on your weight and height. It helps to gauge if you are underweight, at a healthy weight, overweight, or obese.

2. How is BMI calculated?

BMI is calculated by dividing a person’s weight in kilograms by the square of their height in meters. For example, BMI = weight (kg) / [height (m)]².

3. Why is BMI important?

BMI is important because it provides a simple, general indication of your body fat and potential health risks. It helps in identifying if you are at a healthy weight, underweight, or overweight.

4. What are the BMI categories?

  • Below 18.5: Underweight
  • 18.5–24.9: Normal weight
  • 25–29.9: Overweight
  • 30 and above: Obese

5. Are there limitations to using BMI?

Yes, BMI does not account for muscle mass, bone density, and distribution of fat. It may misclassify athletes with high muscle mass as overweight or obese and may not accurately reflect body fat in older adults who have lost muscle mass.

6. What should I do if my BMI indicates I am overweight or obese?

If your BMI indicates that you are overweight or obese, consider consulting with a healthcare provider for a comprehensive health assessment and personalized advice on diet, exercise, and lifestyle changes to improve your health.


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