How Does BMI Index Work?

BMI Index

BMI Index

Kaitlin Floyd

Kaitlin Floyd
Kaitlin Floyd

Updated on 3/18/2023

The body mass index, also known as BMI index, is a method that professionals in the medical field use to determine the amount of body fat. That is present in an individual by using the individual's height and weight measurements as inputs into the formula for calculating the body mass index. The body mass index (BMI) method is another name for this strategy. It is feasible that it will be helpful in establishing the factors that put an individual at risk for a range of health disorders. If so, then this would be a good thing. The body mass index, which is commonly known as BMI, is not necessarily a good indicator of an individual's overall level of fatness. That is because BMI takes into account a person's height and weight.

What Is Body Mass Index (BMI)?

BMI Index

BMI Index

Body mass index, often known as BMI, is a screening technique that is used in medicine to measure the percentage of a person's body that is constituted of fat by calculating the ratio of that person's height to their weight. This ratio is referred to as the body mass index (BMI). You can use the following calculation to determine this information: height in meters divided by weight in kilos. A patient's body mass index (BMI) can be determined by taking the patient's weight in kilograms (kg), dividing that number by the patient's height in meters squared, and then multiplying that result by 703. A BMI (m2) can then be calculated in such a way that medical practitioners will be able to determine the weight of a patient.

The body mass index (BMI) is a way of figuring out how healthy or unhealthy an individual is and to determine how much fat they have on their bodies; the higher the number, the greater the possibility that you have a certain amount of body fat; however, this correlation is not always accurate. Body mass index measures a person's weight about their height and is expressed as a number. The body mass index is a measurement that determines a person's weight about their size and weight. Calculations of body mass index (BMI) obtained by themselves are insufficient to decide on health problems. The body mass index, also known as BMI, is one of the tools and examinations that medical practitioners typically utilize in addition to other resources when determining the general health state of a patient and any potential dangers that may be present. Other resources include:

There is a connection between having a high percentage of body fat and an increased risk of developing cardiovascular disease, stroke, and type 2 diabetes. That is because having a high percentage of body fat makes the body less efficient at burning calories. It is highly likely that malnutrition is the cause of the extremely low percentage of body fat that you have. It is easier for your body to absorb nutrients like vitamins and minerals when there is a healthy mix of muscle and fat, and this is because power has a higher density than fat. In addition to these benefits, it also acts as a source of energy for your body, helping keep your body at a healthy temperature and protecting your internal organs from damage.

BMI Index

BMI Index

If you want to determine whether or not a child or teenager has the appropriate weight for their age group, you shouldn't use a typical BMI chart like you would for an adult. Have a conversation with the medical practitioner caring for your child about the acceptable weight range for someone of their age and height. That will help ensure that your child stays within a healthy weight.

What Is BMI Used For?

The Body Mass Index (BMI) is a measurement used by medical practitioners to diagnose many different types of weight disorders and as a screening device for several health conditions. This index is calculated by considering the patient's height and weight. 1973 was the year that saw the inception of the BMI.

Diagnosing Weight Types With BMI

Commonly, the following ranges of body mass index (expressed in kilograms per square meter) are used to classify the many different sorts of weights that you can find:

  • A weight that is below 18.5 percent of one's ideal weight is considered to be underweight.
  • The optimal zone is somewhere between 18.5 to 24.99, although it might be anywhere in that range.
  • One is deemed overweight if they are between the ages of 25 and 29.9 years old.
  • For someone to be considered obese in Class I, their age must fall between 30 and 34.9 years.
  • A person's Body Mass Index (BMI) must be between 35 and 39.9 for them to be classified as obese according to the criteria of Class II.
  • According to the criteria for Class III obesity, a person's body mass index must be equal to or greater than 40 for them to be classified obese.

BMI Index

BMI Index

The body mass index, commonly known as BMI, is not the only tool doctors and other medical professionals use to discern the various types of weight. Other tools include: The following is a list of other examples of different kinds of instruments:

  • They measure the individual's waist circumference to get their waist size.
  • It is a method of determining the thickness of your skin by measuring the thickness of your skin in specific parts of your body, such as the back of your upper arms and the area just beneath your shoulder blades, using a skinfold caliper. This test is often used to diagnose skin cancer and is frequently used in the diagnostic process for skin disorders, including eczema.
  • The DEXA scan and the air displacement plethysmography (also known as ADP) are examples of diagnostic procedures that are utilized significantly less frequently compared to other available choices.

Screening For Health Risks With BMI

If you have a body mass index (BMI) that is less than 18.5 (which indicates that you are underweight), then you may have an elevated risk of having any of the illnesses that are listed below:

  • Malnutrition.
  • Anemia.
  • The reduced immune system may increase the risk of routinely acquiring infections and illnesses and the likelihood of dying from these conditions. The lowered immune system may also increase the possibility of regularly developing diseases and illnesses.
  • Osteoporosis.
  • Infertility.

BMI Index

BMI Index

If you are underweight, your doctor will probably request specific blood tests and other tests to examine your overall health and determine whether or not you are malnourished. These tests will help determine whether or not you are undernourished. You will do this to establish whether or not you are in danger of developing major health complications, and the test results will be presented to you. It is necessary for you to go through this procedure so that a diagnosis of an eating disorder may be made.

If your body mass index (BMI) is higher than it should be, you have a greater risk of developing health conditions such as those that are described below:

  • Medical conditions that have an impact on the cardiovascular system.
  • The medical term for hypertension is more widely known as blood pressure (hypertension).
  • Diabetes type 2 diabetes
  • Gallstones.
  • Osteoarthritis.
  • Sleep apnea.
  • If you avoid eating specific foods, you may reduce your risk of developing some types of cancer, including those that affect the colon, breasts, endometrium, and gallbladder.
  • Conditions related to mental health, including major depressive disorder and a myriad of other issues

It is essential to remember that even if your body mass index is standard, you still have a high risk of developing any of the health problems you discussed earlier in this paragraph. As an essential consideration, It is a good idea to always keep this in the back of your mind at all times. It is still possible to have a high BMI while not suffering from any of the diseases listed above even if you lead an extremely active lifestyle. That is the case even if you are fit. The manifestation of these disorders is significantly impacted by several factors, including hereditary predisposition and environmental and lifestyle behaviors, such as smoking cigarettes.

BMI Index

BMI Index

Suppose your body mass index (BMI) indicates that you may be overweight. In that case, your healthcare practitioner will probably suggest a battery of blood tests to analyze your overall health to determine whether or not you have an obesity-related condition. These tests will examine your cholesterol levels, glucose levels, liver function, and other factors. In addition, it's feasible that these tests will include a thorough metabolic panel and a lipid panel.

How Do I Calculate My BMI?

Your body mass index (BMI) can be calculated by following these steps, which will walk you through the process:

  • Simply multiplying your current weight in pounds by 703 will allow you to convert it to your weight in kilograms.
  • Simply divide that number by the sum of all the inches that make up your height, and you will have the solution (there are 12 inches in 1 foot).
  • The solution can be discovered by dividing the previous result by your height in inches to obtain the correct answer.

The following is an example of calculating a person's body mass index (BMI). If a person weighs 180 pounds and has a height of 5 feet and 5 inches, giving them a total height of 65 inches, then their body mass index (BMI) may be determined as follows. The individual's overall size is 65 inches in this illustration.

BMI Index

BMI Index

1. 180 x 703 = 126,540.

2. 126,540 / 65 = 1,946.769.

3. 1,946.769 / 65 = 29.95.

Their body mass index, often known as their BMI, is projected to be 29.9.

What Is A Healthy BMI?

If an individual's body mass index is within the range of 18.5 to 24.9, they are regarded to have a healthy body mass index (BMI). According to professionals, this is when things become interesting.

It is of the utmost significance to remember that the quantity of fat a person carries on their body is not the only factor that determines their overall health. That is one of the most important things to keep in mind. Your genes, the amount of time you spend physically active, and whether or not you smoke cigarettes or other tobacco products. The amount of alcohol you consume and any mental health conditions you may have can all impact your overall health and the likelihood that you will develop specific medical conditions.

What Are The Limitations Of BMI?

The typical chart for calculating body mass index (BMI) contains several flaws, which you can ascribe to various factors. Because of this, it is of the utmost importance to ensure that your body mass index (BMI) does not draw an abnormally high level of attention.

BMI Index

BMI Index

The Body Mass Index (BMI) chart is still used by experts working in the medical field today, even though it provides an erroneous value for some individuals. That is because it is the only way you can determine the proportion of a person's body composed of fat, and it is also the most accurate method you can use to do so. Moreover, it is the only one that is now available on the market.

Limitations Of BMI As A Tool For Weight Type Diagnosis

When it comes to making diagnoses regarding different types of weight, the typical BMI has a range of shortcomings, some of which include the following:

  • The body mass index, also known as BMI, does not differentiate between the amount of fat mass and lean body mass that a person possesses. The total weight of everything in your body besides fat is referred to as your "lean body mass," and it is measured as a percentage of your entire body weight. Because of this, a person might have a high body mass index (because they are muscular) while still having a relatively low-fat mass, and the contrary is also true. Athletic people tend to have a higher body mass index than those who are predominantly fat. People who are generally muscular tend to have a body mass index greater than those who are mostly obese.
  • Although individuals classified as female at birth (AFAB) have a higher percentage of body fat than those classified as male at birth (AMAB), the BMI chart used for adults is the same for both categories of individuals.
  • The graphic supposed to depict the Body Mass Index has yet to be updated to reflect the gradual but consistent rise in adult height over the last few decades, even though the BMI has been around for a long time.

BMI Index

BMI Index

You shouldn't use the conventional chart for measuring BMI if you are interested in learning how much body fat any of the following groups have because it doesn't apply to them:

  • Athletes and bodybuilders are included in this category of people. 
  • Children and teenagers.
  • Pregnant folks.
  • Individuals at least 65 years old but have yet to reach 100.
  • People whose medical issues have a direct cause-and-effect relationship with their loss of muscle mass and atrophy.

Limitations Of Using BMI As A Health Condition Screening Tool

When it comes to its application as a screening tool for the risk of specific health diseases, such as type 2 diabetes and heart disease, the body mass index (BMI) has several drawbacks that need to be considered. Some examples of these restrictions are as follows:

  • The body mass index does not consider the location of fat on the body or how fat is distributed over the body. That is a problem because the accumulation of excess fat in certain areas of your body, such as in your belly (abdomen), is associated with a higher risk of health conditions than the accumulation of excess fat in other areas of your body, such as in your thighs. That makes the accumulation of excess fat in your belly (abdomen) a more significant concern than the accumulation of excess fat in your thighs. Because of this, you have a higher chance of having several health disorders. That is a problem because the accumulation of excess fat in your thighs is associated with a higher risk of health conditions than the accumulation of excess fat in your belly is associated with a lower risk of health conditions. That is a problem because the accumulation of excess fat in your stomach is associated with a lower risk of health conditions (abdomen).
  • Other factors, such as a family history of diabetes, high blood pressure, cardiovascular disease, and high cholesterol (dyslipidemia); familial longevity (average lifespan); or a family history of cancer, are commonly overlooked in the link between BMI and death rate. However, data suggests that these additional factors may have a role in the relationship between BMI and death rate. However, some data suggests that these additional factors may have a role in the connection between BMI and death rate.


BMI Index

BMI Index

The body mass index commonly referred to as BMI index, is a simple measurement that medical professionals can use to assess a patient's potential sensitivity to various health issues. When a patient's body mass index (BMI) is high, the patient's chance of developing health problems is also significant. The Body Mass Index (BMI), on the other hand, is not the sole factor determining whether you are healthy overall. It only sometimes provides an accurate evaluation of body fat. In addition, other aspects of your life contribute to the overall picture of your health that emerges from the equation. You should discuss these topics with your primary care physician or another trained healthcare professional if you have any questions or concerns about your weight or risk of getting certain health illnesses like heart disease. They are there at any time to provide a helping hand to whatever may be requested of them.

Frequently Asked Questions

Is there a normal BMI?

If your body mass index (BMI) is between 18.5 and 24.99, you have an average body mass index or are within the Healthy Weight range. If your body mass index (BMI) falls between 25.0 and 29.9, you are regarded to have an unhealthy level of excess fat. No matter how old you are, if your body mass index (BMI) is 30.0 or greater, you are deemed obese.

What is the formula for calculating BMI in kilograms and centimeters?

To determine a person's body mass index using the metric system, divide their weight in kilograms by the square of their height in meters. That will give you the body mass index. You can use a different calculation method because size is typically measured in centimeters. This method is as follows: first, the weight in kilograms is divided by the height in centimeters squared; second, the result is multiplied by 10,000; and third, the answer is expressed as a percentage.

What is the best way to calculate BMI manually?

After that, calculate your body mass index (BMI) by taking your weight in pounds (lb) and dividing it by the square of your height in inches (in), then multiplying the result by a conversion factor of 703. That will give you your BMI. If you use a handheld calculator with a square function, divide the weight in pounds by the square of the height in inches, multiply the result by 703, and then round the result to the nearest whole number. That will give you the size in inches.

How should a 70-year-old woman's BMI be calculated?

Most medical professionals agree that adults should aim to maintain a body mass index (BMI) that falls between 18 and 24.99. For adults, having a body mass index (BMI) greater than 25 is considered obese. On the other side, people in the best health are those above the age of 65 and have a body mass index (BMI) that falls within the ranges of 25 and 27. According to the findings of a study that was carried out, those over the age of 65 with a low body mass index have a lower life expectancy and are at a greater risk of acquiring various health issues.

What should my weight be in kilograms?

The World Health Organization (WHO) has established that a body mass index (BMI) ranging from 18.5 to 25 is considered healthy, and this range applies to both boys and girls. Using the BMI scale, it is possible to determine a healthy weight that corresponds with any particular height, and the British Medical Association developed this scale.

What is the reason that BMI is not accurate for elderly people?

The BMI can provide an inaccurate body fat reading in athletes and other individuals with a muscular build. It is also possible for individuals who are elderly or who do not have a significant amount of muscle tissue to have an inaccurately low estimation of their body fat percentage. Even though the BMI can be used on most adults, it has significant restrictions.