Is BMI still relevant?

Is BMI still a relevant measure of health?

BMI is an easy and consistent general measure of health that has been used extensively over the years, because it requires:

• 1 variable, weight (kg),
• 1 piece of equipment, a reliable set of scales

A high BMI (>25kg/m2) has consistently shown to be an increased risk factor for chronic diseases such as :

• Heart and blood vessel disease
• High blood pressure (hypertension)
• Type 2 diabetes
• Osteoarthritis, especially in the hips and knees
• Certain types of cancer, such as colon and breast cancer
• Depression and other mental health disorders
• Gallbladder disease

BMI is a good measure of general body composition, but falls down in the 2 following main scenarios:

• Overestimated body fat for large framed men OR trained individuals with a low body fat percentage. The average body fat percentage for
  • Women are 25-31%
  • Men are 21-24%,

However, excellent amounts are:

• • Women are 18-24%
  • Men are 14-20%

Muscle mass is denser than body fat and, as a result, BMI overestimates the health risk for such individuals. It doesn’t take into account the health benefits of the higher muscle mass, such as improved glucose control and improved overall body strength.  However, measuring body composition requires sophisticated equipment. Equipment such as a DEXA scan or using equations to estimate composition using body fold measurements, which, has its own set of errors.  In general, using body fat percentage is a more important measure of health, but be aware, it also has errors.

The best approach would be to use body fat % measurements but understanding there will be errors. However, we can measure the change over time to really see if you are making progress.

Finally, a very simple and reliable measure of health is waist circumference. This only requires a tape measure.

Abdominal fat (belly fat) is consistent and correlates well with increased disease risk for chronic diseases, such as heart disease and diabetes.

A good number for waist circumference is:

• • Women <80cm
  • Men are <94cm

High numbers are considered:

• • Women: 81-88cm is an increased risk,  88+cm is a substantially high risk
  • Men: 94-102cm is an increased risk,  102+cm is a substantially high risk