WHAT IS BMI?
The body mass index, or BMI, is a metric used to estimate the amount of body fat a person has.
Though BMI doesn’t measure body fat directly, it correlates with other direct measures of body fat, according to the Centers for Disease Control and Prevention (CDC).
Only two measurements are involved in BMI: height and weight. To calculate your BMI using pounds and inches, divide your weight by your height squared, and then multiply by the conversion factor of 703. (The calculation is the same using kilograms and meters, except no conversion factor is needed.)
For example, a person who weighs 130 pounds and is 5 foot, 6 inches (66 inches) tall would have a BMI of 20.9: 130 / (66 x 66, or 4,356) x 703 = 20.9.
On the BMI scale, anything below 18.5 is considered “underweight,” 18.5 to 24.9 is “normal,” 25.0 to 29.9 is “overweight” and an index of 30 or more is “obese.”
In the health care setting, physicians use BMI to gauge if their patients are at risk for certain health issues.
For example, studies have shown that people with BMIs of 30 or more have increased risk of death from a number of diseases, including heart disease, diabetes and colorectal cancer. There are also issues with being underweight on the BMI scale, such as increased risk for malnutrition, osteoporosis and anemia.
In recent years, many experts have expressed their doubts about relying too much on the body mass index, stressing that it is not an accurate measure of body fat or health.
One reason is that BMI does not take into account age and sex. Women tend to have more body fat than men of the same BMI, and older people tend to have more body fat than younger people of the same BMI, according to the CDC.
Additionally, BMI has no way of measuring where body fat is located in the body. Studies have shown that belly fat — fat around the abdominal organs — is far more dangerous than the peripheral fat beneath the skin in other areas of the body.
Finally, BMI doesn’t consider bone density or muscle mass — highly trained athletes may have high BMIs because of increased muscularity.
To correct for the index’s shortcomings in determining a patient’s risk of disease, the National Heart, Lung, and Blood Institute recommends using two other predictors in addition to BMI: waist circumference and risk factors associated with obesity, such as high blood pressure and physical inactivity.
There are numerous online BMI calculators. Alternatively, you can use these equations:
- English BMI Formula BMI = [(Weight in Pounds / ( Height in inches x Height in inches )] x 703
- Metric BMI Formula BMI = Weight in Kilograms / ( Height in Meters x Height in Meters )
On completion of the calculation, you should have a result between 15 to 40, although some very under or overweight individuals may score outside of these parameters. The lower end of the scale suggests that you are underweight while those on the higher end of the scale are considered overweight; 18.5 to 25.0 is deemed to be healthy.
WHAT ARE THE BENEFITS OF A LOW BMI?
Body mass index, also called BMI, is a calculation of a correlation between a person’s height and weight that categorizes him or her as underweight, of normal weight, overweight or obese, assuming a normal body composition. Underweight is considered a BMI of 18.4 or lower. A BMI of normal weight is any number between 18.5 and 24.9. The overweight range is between 25 and 29.9, with anything above that being considered obese. Maintaining a low BMI is important for normal health, growth and functioning of your body.
According to the Centers for Disease Control and Prevention, or CDC, if measuring in pounds and inches, the formula to obtain your BMI is to divide your weight by your height squared and multiply by 703. For example, a person who is 5 feet 4 inches tall that weighs 160 pounds will first convert her 5 feet into inches and add the 4 inches to arrive at a total of 64 inches in height. The equation then becomes the product of 160 divided by 64 inches squared (160 divided by 4096), multiplied by 703, which equals a BMI of 27.46.
Naturally, one of the main benefits of having a normal BMI would be that of maintaining a healthy weight. Maintaining a normal BMI will require a person to eat well-balanced meals and exercise regularly, which will further increase overall health. Being of a healthy weight has many benefits, such as looking and feeling better, as well as increased confidence and energy.
Lowered Risk of Health Complications
The CDC states that overweight and obese people have an increased risk of suffering from heart disease, stroke, some cancers, type 2 diabetes, joint problems, chronic inflammation, and various other health conditions. To obtain or keep your low BMI, you have to eat well and exercise. In addition, a healthy body weight makes a more fit body and a more lifestyle more attainable and maintainable.
Desirable Physical Appearance
Even though the BMI calculation does not take into account actual body fat percentage, it is more than likely that if you’re in the normal weight zone, you are going to be happy with how you look. For most, when you are happy with how you look, you will want to stay that way. With confidence comes a better outlook on life and overall happiness in your day-to-day life.
BODY MASS INDEX ADVANTAGES & DISADVANTAGES
There are many ways to assess your weight and body composition to determine if you’re carrying too much body fat. Some methods, such as skin fold caliper testing, are quite invasive while an MRI, which is very accurate, may not be readily available. Body mass index, BMI for short, compares your height to your weight and is often used by healthcare professionals as a convenient way of assessing whether your weight is healthy.
Advantages of BMI Testing
BMI testing, unlike many of the other methods used to assess weight, requires no special training. Although the calculation may seem complicated on first view, with practice it can be completed easily in just a few moments. The results are easy to understand; it’s simply a matter of looking up your score on a standardized chart. BMI testing does not require you to remove any clothing, other than your shoes when you weigh yourself, which makes it ideal for users who might otherwise be put off by a more invasive procedure.
Disadvantages of BMI Testing
Your body weight includes a number of components, such as muscle mass, fat, internal organs, water and skeletal weight. BMI does not differentiate between these components, so some populations will score badly when, in fact, they are quite healthy.
Muscle and bone weigh significantly more than fat, so it’s possible to be heavy but still carry a low amount of body fat. This is often the case for football players, competitive weightlifters, those with large skeletal frames and other very muscular people.
BMI provides a quick snapshot of your weight in relation to your height. However its limitations mean that if you want a more personalized and accurate result, BMI should be used in conjunction with other tests, such as underwater weighing, bio-electrical impedance or a skin fold caliper exam, which will reveal how much of your weight consists of fat.