When people think of body composition, thoughts of fat come to mind. However, fat is only one part. Body composition is actually the proportion of all the tissues that make up your body – adipose, muscle, bone, and water. There are many ways to measure body composition that vary in accuracy and reliability.
Body mass index, or BMI, is a simple calculation made from a person’s height and weight. It is not a direct measure of body fat. Despite it not being a direct measure of body fat, BMI is widely used to identify people that are “overweight” or “obese”, typically as a risk factor correlating with cardiovascular and metabolic disease risks.
Higher BMI is certainly not the only thing related to the above mentioned health problems.
Calculate your BMI
There are two ways to calculate your BMI, depending on whether you are accustomed to imperial or metric units. First, you must measure your weight and height.
Use the following steps for imperial units:
Step 1: Multiply your weight in pounds by 703
Step 2: Divide that number by your height in inches
Step 3: Divide that number by your height in inches again
Here is an example for someone that weighs 175 pounds and is 5’11” (71 inches) tall.
Step 1: 175 x 703 = 123025
Step 2: 130055 / 71 = 1732.75
Step 3: 1831.76 / 71 = 24.41
Use the following steps for metric units:
Step 1: Square your height in meters (m2)
Step 2: Divide your weight in kilograms (kg) by your height m2
Here is an example for someone that weighs 79.5 kilograms and is 1.8 meters tall.
Step 1: 1.8 x 1.8 = 3.25
Step 2: 79.5 / 3.25 = 24.46
This person’s BMI is about 24.4 kg/m2. If you refer to the classification mentioned below, this person is considered to be in the “healthy weight” range.
The Centers for Disease Control (CDC) provides a great online BMI calculator as well as some additional resources here: https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html
A person can be classified into one of the weight categories in this Table based on their BMI. The categories in this table are based on the World Health Organization standards.
Measure your height
A stadiometer is a tool used to measure height. If you do not have access to one, stand straight against the wall. Have someone else put a mark on the wall at the top of your head. Then measure the distance between the floor and the mark.
Limitations of BMI
BMI is simple and easy to calculate, but it comes with several limitations including :
Limitation 1: BMI does not differentiate between body fat and lean mass. In fact, we have seen numerous participants in research or clients in practice who have had a healthy BMI. However, following a more comprehensive body composition assessment, they have excessive body fat coupled with low muscle mass. On the other hand, we have tested elite athletes who were extremely muscular, but BMI classified them as “obese” when they are actually lean. In the end, BMI can sometimes misclassify people.
Limitation 2: BMI does not take into account body fat distribution patterns- where people tend to store fat in specific regions of the body. This is a problem if a person distributes body fat in a particular area. For example, if a person’s BMI is less than 30 kg/m2 but their waist circumference is high, they can still be at risk for unfavorable health outcomes. The reason for this is that fat storage in the abdominal (or visceral) region is the main concern for developing chronic diseases. This type of fat distribution is referred to as “android.” Therefore, a person can actually be considered “healthy” by BMI standards, but still be considered obese if their waist circumference is too large.
Limitation 3: BMI may not be very useful for tracking changes in body composition with aging. Muscle mass tends to decrease through the years, especially if a person does not exercise. This problem is referred to as sarcopenia. The loss of muscle tissue is often replaced with unhealthy fat. This can result in no change in body weight and BMI even though body fat percentage increases.
Limitation 4: Though BMI is linked to the cardiovascular and metabolic diseases, its relationship is not nearly as strong as an actual measure body fat percentage.
MADE versus BMI
Even though BMI has many limitations, it is simple. All that is required is height and weight, as well as the ability to perform the calculations. Because of this, BMI is one of the most commonly used methods to identify individuals who may be obese. Users beware: diagnostic accuracy is sacrificed for the sake of simplicity with BMI.
However, the MADE app has revolutionized the fitness industry by providing a method that is both accurate and simple. All that is required is for you to enter your height and weight while setting up your user profile. Instead of calculating your BMI by hand, all you have to do is simply take the picture. Accurate measures of body fat percentage, fat mass, fat-free mass, android and gynoid fat distribution are automatically calculated and displayed right on your smartphone’s screen. The MADE app will give a much more detailed body composition profile than an inaccurate BMI value, which has little meaning beyond weight-to-height ratio.
The limitations of BMI presented above do not exist with MADE. We developed the MADE App to provide one of the most accurate measures of body composition available, in the palm of your hand. We wanted to give you a few of the strengths of the MADE App:
Strength 1: MADE provides a complete and accurate body composition profile for any body size and BMI level.
Strength 2: MADE provides a direct estimate of body fat percentage, fat mass, fat-free mass.
Strength 3: MADE provides you with information about your body fat distribution patterns, in both the android and gynoid regions.
Strength 4: MADE provides a reliable and accurate tool for tracking changes in body composition, throughout the lifespan and with exercise training. It provides an easy method for monitoring how body composition changes over time.
The precision of MADE over BMI is clear when both are compared to the “Gold Standard” laboratory 4-compartment model. This study was performed among a large sample of male and female subjects (n=182) across a wide age range. All subjects were tested with the 4-compartment model, which included the following sophisticated techniques: dual-energy x-ray absorptiometry to measure bone content; underwater weighing to measure body volume; and bioimpedance spectroscopy to measure total body water. The subjects also had their height and weight measured to determine BMI, as well as having their body composition estimated from the MADE app image processing method.
We compared BMI and the body fat percentage values from MADE to the 4-compartment model with a statistical measure called correlation, which determines the strength of a relationship between two variables. Like we talked about in some of our previous posts, correlations can range from -1.0 to +1.0, with values close to zero indicating a weak relationship. Values above 0.80 are described as “strong,” and other researchers describe correlations above 0.90 as “nearly perfect.” These data show BMI and %Fat showed a correlation of 0.10, which was not statistically significant and is considered very weak. On the other hand, MADE displayed a statistically significant correlation of 0.89, which is considered very large. The Figures below provide a visual comparison of these relationships.
Though the simple height-to-weight ratio value provided by BMI is commonly used to evaluate body composition, it does not correlate very well to actual body fat percentage obtained from the “Gold Standard” 4 compartment model. However, not only is the MADE app as simple as BMI, it is much more accurate and provides a practical alternative to the 4-compartment model. In addition, the app is downloaded to each user’s smartphone and hence each test is private. Unless a user choses to share the information, he or she is the only person to see their own results.