Your Health Is Not Just a Number: Part 2 | Health
Read Part 1 here.
The biggest flaw of BMI, or body mass index, is it does not consider a person's body fat versus lean tissue or muscle content. Fat is actually lighter than muscle.
Dr. William McArdle, Professor Emeritus for the Department of Family, Nutrition, and Exercise Science at the Queens College of the City University of New York, stated in his book, Exercise Physiology, that if you compare same-size portions, muscle will weigh more than fat since it is denser. The density of muscle is 1.1 g/mL, while that of fat is only 0.9 g/mL. This means that on average, 1 liter of muscle weighs 2.3 lbs or 1.06 kg, while 1 liter of fat weighs 1.98 lbs or .9 kg.
As you can recall in part 1 of this article, BMI is the measurement of body fat content based on the height and weight of a person. It does not take into account overall body composition, bone density, muscle mass, gender, and racial differences, which are all indicators of health. Therefore, it will classify athletic people, who are often muscle-bound and thus are heavier, as fat when they’re actually not.
Measurements for BMI indicate:
- - Normal weight = 18.5 to 25 BMI
- - Overweight = 25 to 30
- - Obese = 30 and above BMI
For example, a 6ft-tall sedentary person weighing 90kg (200lbs) may have the same BMI (26) as an Olympic 100 meter sprinter of the same height and weight. This also means that both these guys are overweight, based on their BMI. While the calculation may be correct for the sedentary person, it’s incorrect for the athlete.
What’s Better than BMI
Former Science Director and independent consultant of the British Nutrition Foundation, Margaret Ashwell, explained at the 19th Congress on Obesity held in France, that a superior predictor than BMI is a person’s waist-to-height ratio (WHtR). She and her colleagues believe that it’s easier to keep your waist circumference to less half your height than rely on your BMI. She further said,
According to the nutrition scientist, WHtR should be considered as a screening tool because BMI does not consider the distribution of fat around the body. For example, abdominal fat affects organs like the heart, liver, and kidney more severely than fat around the hips or bottom. WHtR can help you know what your abdominal fat levels are, an information that BMI cannot provide.
Looking back at our 6ft-tall (72 inches) sedentary person and athlete example, if the former has a waist of 40 inches and latter has 34 inches, we can confirm that the athlete is within a healthy weight, while the sedentary person is overweight. This is because the sedentary person has a waist circumference that is more than half his height, while the athlete is within half of his height.
Risks of Unhealthy Waist Size
Regardless of BMI, waist size is strongly associated with type 2 diabetes and other diseases linked to it. This is according to researchers from the Medical Research Council (MRC) Epidemiology Unit in the UK. The study, published in PLoS Medicine and led by Dr. Claudia Langenberg, suggested that it’s easy to determine whether a person is at risk of type 2 diabetes by measuring one’s waist circumference.
This is one of the main reasons why waist-to-height ratio is better than BMI. Unfortunately, authorities such as the National Institutes of Health (NIH) and Centers for Disease Control and Prevention (CDC) still promote the use of BMI. However, after reading this, you know better! ;)
To learn more about BMI, visit the Aussie Supps Nutrition Hub. We have our in-house nutritionist to take care of your health and diet needs. Our in-house nutritionist uses tape meaurements as well as body composition scales to give accurate readings of muscle mass, body fat, bone mass and the amount of visceral (dangerous) fat a person has - meaning that nutrition can be tailored very specifically to a persons body composition!
Exercise Physiology. https://books.google.com.ph/books/about/Exercise_Physiology.html?id=XOyjZX0Wxw4C&redir_esc=y
Calculate Your Body Mass Index. https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm
About Adult BMI. https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html