For years we have been categorized as either underweight, normal weight, overweight or obese following the use of one mathematical equation, Body Mass Index (BMI). However, it is important to take the results of this equation with a pinch of salt, as it is an unreliable system used to tell you how fat you are.
BMI is a mathematical equation that divides your weight by your height and gives you a number that doctors use to measure whether you are healthy, overweight or obese. The results of your BMI score are determined as follows: below 18.5 is underweight; 18.5 to 24.9 is normal; 25 to 29.9 is overweight; and 30 or higher is obese.
This system that is used worldwide is however, very unreliable as it does not take into account the relative proportions of bone, muscle and fat in the body that make up your weight shown on the scales.
Since muscle and bone is much denser than fat, anyone who is active is going to have more weight in muscle than the average person. Consequently, your BMI may not accurately represent your health and fitness, or how healthy and fit you look.
So it is often seen that those people with a slightly higher proportion of muscle than others may come out with a higher BMI, but may actually be fitter and healthier than those who have lower BMI.
At this point, I then take you towards body fat percentage. Body fat percentage is just like it says, measuring what percentage of your body is made up of fat. This helps to give us a more accurate representation of how ‘fat’ and healthy we are, whether we are active or sedentary.
Let’s put all this information into practice:
Victoria and Mandy are both 5 foot 5 inches and 65kg, this means they will both have a BMI of 24 which is within the healthy range.
Mandy doesn’t work out and eats junk food. She just controls the portion sizes of her junk food, and that keeps the weight on the scales down. Mandy has 19.5kg of fat and 45.5kg of lean mass, thus meaning she is 30% body fat.
Victoria does a weight training workout and cardio 3 times per week and eats a healthy diet. Victoria has 13kg of fat and 52kg of lean mass. This would put Victoria at 20% body fat.
From this we can see that despite being the same height, weight and BMI, they have completely different looking bodies, which is shown by their body fat percentages being at totally other ends of the spectrum.
Consequently, it would be a mistake to rely solely on BMI as an indicator of how healthy and fit you are. It may be useful if you are not working out or in the early stages of working out regularly to track your progress. BMI also promotes the whole ‘you’re a success or a failure depending on what the scales say’ philosophy.
To accurately track your progress in terms of health, fitness and leanness body fat percentage is the best gauge for you to follow.
Kristian