Understanding the BMI Formula

understanding bmi formula

Much has been made about the Body Mass Index and the BMI formula since it was first introduced over a decade ago. Many doctors believe that this formula is the key to accurately assessing your body’s fat percentage and to predict whether or not you are at risk of contracting weight-related diseases such as stroke, heart disease, and type two diabetes. These conditions are some of the most deadly diseases in the United States and understanding your personal risk can help you determine which actions you may need to take in order to reduce your risk.

Chances are that whether you are overweight, underweight or at a healthy weight, you already have some idea of the condition of your body. That said, using the BMI formula to assess your Body Mass Index can help pinpoint the exact state of your health. You may know that you need to lose a few pounds, for example, but you may not know that you are medically obese. On the other hand, many people who consider themselves obese are pleased to find out that they are actually only overweight. This knowledge can encourage them to take the few extra steps needed to put them down to a healthy weight. Those who have borderline eating disorders may also be surprised to learn that they are considered to be underweight by medical professionals.

Both weight loss and weight gain tend to be gradual. They can be so gradual, in fact, that it can be hard to notice just how much your body has changed if you only look in the mirror each day. Although weighing yourself can help you asses how much you have changed, it does not always give you the full picture. Your height must also be taken into consideration when you are judging the health of your body. A very small person, for example, may only be able to gain a few pounds before they become overweight. A taller person, on the other hand, may be able to gain twenty or thirty pounds before they move from the healthy weight category into the overweight category. If you are trying to accurately judge your health, your risks and your percentage of body fat, the BMI formula may be exactly what you are looking for.

How Do You Calculate Body Mass Index?

Using the body mass formula is fairly simple, as long as you have a couple of pieces of information. First, you will need to weigh yourself. Although the weight of most clothing is negligible, you should remove any heavy shoes or sweaters before getting on the scale. For the most accurate results, you should weigh yourself without wearing any clothing at all. Once you have a current weight number, you need to make sure that you have an accurate height number as well. Take off your shoes when you measure your height and push down your hair as much as possible. Remember that the more accurate the numbers are, the more accurate your BMI reading will be. When calculating the height for the BMI formula, it is important that you measure strictly in inches, not in feet and inches as is normally done when calculating height. If you are five feet ten inches tall, for example, your height is seventy inches.

The BMI formula itself can be phrased in a number of ways. Although the numbers and the results are always the same, different people find it easier to calculate the formula if the number is put in different orders. Regardless of the order, however, the first thing you will need to do is square the number of your height. In order to square your height, simply multiply the number by itself. If you are eighty inches tall, for example, your height squared will equal 80 x 80, or 6400.  Now you have two of the three numbers you will need for the equation: your weight and your height, squared. The third number you will need is 703. Because the BMI system was first developed using metric calculations, this number is needed to ensure that BMI measurements using the imperial system match metric BMI measurements from around the world. If you measure your weight in kilograms and your height in centimeters, you can skip the third number altogether.

Now that you have your three numbers, it is time to plug them into the BMI formula. Most people use either this formula: BMI=w/h2x703 or this formula: BMI=w(703)/h2. In either case, the numbers used and the results of the calculations are the same. Keep in mind that ‘w’ equals your weight and ‘h2′ equals your height squared. If, for example, you are 80 inches tall and you weight 160 pounds, the formula would look like this: 160/6400×703=17.57 or like this: 160(703)/6400=17.57. In both cases, the results, your BMI, are the same: 17.57.

Understanding Your Results

The basic premise for the BMI formula and its results is simple. A BMI of less than 18.5 indicates that you are underweight. A BMI of 18.5-24.9 indicates that you are at a healthy weight. A BMI of 25.0-30.0 indicates that you are overweight. Finally, a BMI of over 30.0 indicates that you are obese. While these numbers are generally accurate for most people, doctors warn that there are a few things that can skew the results. If you are an athlete, for example, you probably have a much higher muscle mass than the average person. Not only is muscle left unaccounted for in the formula, but it actually weighs more than fat. Regardless of your fat to muscle ratio, the BMI formula reads all weight as though it were made from the average ratio of muscle to fat. On the other hand, those who are the most sedentary, and have the least amount of muscle, such as the ill or elderly, may also see skewed results. The fact that a larger-than-average percentage of their weight comes from fat is not represented in the formula.

It is also important to understand what these results actually mean. In the end, these numbers are simply guidelines invented by doctors and scientists. The difference between an “overweight” BMI and an “obese” BMI may be a single pound. The average person gains and loses around five pounds each day depending on the amount of water they drink and how recently they have eaten or gone to the bathroom. In order to accurately calculate your BMI, you may want to weigh yourself over the course of a few days and use the average in your calculations.

Additionally, your Body Mass Index is not a definitive measure of your overall health. Instead, it is an indication of how likely you are to contract weight-related diseases in the future. Many things contribute to the state of your health. Your Body Mass Index is only one factor, albeit an important one. The BMI can also be used as an indication of whether or not teens and older children are on track in terms of their growth. It is important to remember, however, that children are still growing and that their BMI can change drastically in only a few weeks or months. The BMI is a guideline that can help you determine whether or not you are at a healthy weight. The most important thing to remember is that it, and your overall health, can be changed. By using the BMI formula as a tool and incentive to improve your health, you can live a longer, healthier life.

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