Body Mass Index
The body mass index (BMI) or Quetelet index is a value derived from the mass (weight) and height of an individual. The BMI is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m2, resulting from mass in kilograms and height in metres.
The BMI is an attempt to quantify the amount of tissue mass (muscle, fat, and bone) in an individual, and then categorize that person as underweight, normal weight, overweight, or obese based on that value. That categorization is the subject of some debate about where on the BMI scale the dividing lines between categories should be placed. Commonly accepted BMI ranges are underweight: under 18.5 kg/m2, normal weight: 18.5 to 25, overweight: 25 to 30, obese: over 30.
BMIs under 20.0 and over 25.0 have been associated with higher all-cause mortality, increasing risk with distance from the 20.0-25.0 range.] The prevalence of overweight and obesity is the highest in the Americas and lowest in South East Asia. The prevalence of overweight and obesity in high income and upper middle income countries is more than double that of low and lower middle income countries.
Why Measure Body Fat Percentage?
Whether you liked your result or not, you may wonder why body fat percentage matters. In fact, if your goal is weight loss, you might be tempted to use a simple body weight scale for feedback on your progress. But body fat percentage tells you much more than the scale does.
When you're trying to slim down, boost your health, or increase your level of fitness, fat loss should be your goal, rather than simple weight loss. You want to keep the lean mass, or fat-free mass, that your body needs. This includes bone, blood, connective tissue, organs, and muscle.
Muscle loss sometimes occurs when you are losing weight, but it's not the kind of weight loss you are seeking. You want to maintain muscle mass because it helps your body to function and perform more efficiently, boosts your metabolism, and gives your frame a lean, tight appearance.
By measuring changes in body fat percentage, you can tell how well your fitness or weight loss program is helping you to lose fat while maintaining fat-free mass.