Body Mass Index (BMI) and body composition are two measurements that are used in the healthcare and fitness industries to assess overall health. Each offers a unique insight into the body’s composition but in unique ways.
Let’s break down BMI and body composition, discussing what each one indicates and how to measure them. You can learn more about the differences between BMI and body composition by clicking here.
What is BMI and How is it Measured?
BMI is a measurement of a person’s weight in comparison to their height. It is measured using an equation as follows:
BMI = weight (kg)/height (m)^2
BMI is split into a series of categories, ranging from underweight to obese:
Underweight – BMI less than 18.5
Normal or healthy weight – BMI between 18.5 and 24.9
Overweight – BMI between 25 and 29.9
Obese – BMI 30 or above
To measure BMI, you will need two measurements – weight and height. A stadiometer can be used to measure height, which is a wall-mounted tape measure that extends from the floor to a person’s head to provide a measurement of height in metres or centimetres. To measure weight in kilograms or pounds, you can either use a digital or manual scale.
Square the value you obtained for the height and divide the weight by this number to get to the BMI.
What is Body Composition and How is it Measured?
Body composition refers to the relative amounts of muscle, fat, bone, and water in the body. There are a few different ways to measure it, including the following.
Dual-Energy X-ray Absorptiometry (DEXA)
DEXA scanning machines use low-dose X-rays to measure bone density, lean tissue (muscle) mass, and fat mass. It can be used to assess the full body, providing a well-rounded picture of body composition and overall physical health.
Bioelectrical Impedance Analysis (BIA)
BIA runs a small electrical current through the body and measures the resistance of the body’s tissues to this current. In turn, it provides information about the body’s composition, including muscle and fat tissue.
BIA machines are often found in gyms so you can take some quick measurements after a 10-minute workout. often display graphics of a person’s body to visually display the distribution of muscle and fat throughout the upper and lower body.
Skinfold Callipers
Skinfold callipers measure the thickness of skinfolds in different areas of the body to estimate the amount of subcutaneous fat. Common sites for skinfold measurements or the triceps, lower lateral abdomen, and upper thighs.
The measurements obtained using skinfold callipers can be entered into an equation to estimate a person’s body fat percentage. if needed, the persons lean muscle mass can then be estimated using their weight, height, and estimated body fat percentage.
Measurements are taken at sites like the triceps, abdomen, and thighs, and then entered into equations to estimate body fat percentage.