What are the benefits and drawbacks of BMI?

Body mass index (BMI) is a measure of a person's height against their weight, measured in kg/m2. It’s sometimes used by healthcare professionals or personal trainers to provide insight into an individual’s health.

Whilst BMI can provide some helpful information for an individual and their healthcare team, it’s not always the best option. There are many other metrics that are much more accurate and provide more detailed health-related information about a person than BMI does.

Below, we have discussed the potential benefits and drawbacks of using the Body Mass Index (BMI) metric.

Benefits of using BMI

BMI is quick and easy to measure. To accurately measure your BMI, all you need is your height and weight. You can then plug the figures you get for your height and weight into the equation for BMI or use an online calculator to do it for you.

BMI may be helpful for assessing whether a person is severely underweight or overweight, which can be used on an individual level or population level.

BMI is a widely accepted and known measurement, enabling healthcare professionals within different practices and medical fields to corroborate on a patient’s care.

Drawbacks of using BMI

BMI doesn’t distinguish between fat mass and muscle mass. Since muscle weighs more than fat, an individual with a lot of skeletal muscle mass, such as an athlete or bodybuilder, may rank as ‘obese’ on the BMI scale, despite having very little body fat.

BMI may not be suitable for certain populations, such as athletes with high muscle mass or older adults who may experience muscle loss. It can result in misclassifying individuals with a healthy body composition.

BMI only provides limited insights into the distribution of body fat and doesn't account for variations in fat distribution, which can affect health risks. For example, abdominal fat may pose higher health risks than fat in other areas, but you won’t be able to see this in BMI, which just gives a general estimation of a person’s weight and health.

Two individuals with the same BMI can have different body compositions and fat distributions. Central obesity (fat around the abdomen) is associated with higher health risks, but BMI alone doesn't capture this information.