Any of us who are focused on health or fitness or have been motivated to lose weight in the past have encountered the dreaded BMI.
For many years, we have blindly followed the simple formula of weight divided by height. More often than not, when plugging in details to that online calculator, we feel the dread rising as our bracket expectation is shattered even when we thought we were on track with training.
In many cases, where individuals are inactive and obese, the BMI indicator is a great tool to kickstart a fitness regime to get fit and healthy and avoid disease caused by being overweight. However, for the rest of us who are living healthy lives, being active often and building muscle rather than fat, the BMI scale falls short, and there are many reasons why.
The first limitation is that it is nothing more than a simple mathematical formula based only on basic dimensions. It only assumes low muscle mass and high relative fat content because it was designed around people who have low muscle and high fat. It is not complex enough to consider the large portion of the population that are lean, fit and healthy and whose weight is primarily composed of heavy muscle mass and not fat.
Because the formula only accommodates overall ‘weight’, BMI is also inaccurate as it cannot distinguish between fat, muscle and bone mass. Because muscle tends to be heavier than fat, an individual with little body fat but an abundance of muscle tone can be tipped into overweight status without being at risk of the health risks of obesity.
BMI also does not consider how fat is distributed around the body and how that distribution differs among individuals. Your fat distribution can be affected by age, sex, ethnicity and many other factors, and these have a significant amount to do with determining a healthy weight.
As a solution, there are many other measures of body fat that can be used in conjunction with BMI to get a more clear picture of weight and health. These include skinfold thicknesses, bioelectrical impedance, underwater weighing, and dual energy x-ray absorption. The waist circumference (sometimes divided by height) is also a simple measure of fat distribution.
The best way to ensure that your body fat is measured correctly and monitored is to speak with your GP and work with a trainer in order to get a picture of your body fat and work towards a goal of reducing it to keep healthy.