BMI, or body mass index, was invented nearly 200 years ago. Although it can still be a useful tool for looking at weight trends or obesity rates in large groups, it has some important limitations when it comes to measuring an individual person’s health. Here are a few things to keep in mind when it comes to BMI and your health:
1. BMI is not a measure of body fat.
BMI only compares your weight to your height—it can’t tell you how much of your weight comes from body fat. And when it comes to health risks, body fat percentage can sometimes provide more useful information than a number on the scale.
Tests such as hydrostatic weighing or skinfold measurements can give a better estimate of body fat. If your doctor classifies you as overweight or having obesity based on your BMI, getting more information about your body composition may give you a clearer picture of your health and help track changes over time.
2. It doesn’t fully predict heart health risks.
According to the Canadian Obesity Guidelines, some people with obesity do not show signs of increased metabolic or heart health risks, even though they have a higher BMI.
In simpler terms, having a BMI in the overweight or obese range does not automatically mean you are at higher risk for cardiovascular disease or a heart attack. Other measurements—such as waist-to-height ratio, blood pressure, cholesterol, and triglycerides—can provide additional information about your overall health and risk factors.
3. It doesn’t take into account where body fat is stored.
Where fat is stored on the body can matter when it comes to health. For example, carrying more fat around the abdomen may be linked to greater health risks. BMI, however, does not tell you where body fat is located.
This is why healthcare providers may use BMI along with other measurements, such as waist-to-height ratio, to get a better idea of fat distribution and possible health risks.
4. It doesn’t take muscle mass into account.
Muscle has many health benefits. It can support metabolism, strengthen bones, and help with maintaining weight loss, among other things.
Muscle is also denser than fat, which means a person with a lot of muscle may weigh more even if they do not have a high amount of body fat. Because of this, someone with above-average muscle mass may have a higher BMI that does not accurately reflect their body composition.
If you think muscle mass may be affecting your BMI, your healthcare provider may recommend a test that looks more closely at your body composition.
5. It doesn’t account for differences among individuals and populations.
BMI uses the same basic calculation for everyone. It does not account for differences related to sex, ethnicity, age, body type, or other individual factors that can affect how BMI relates to health.
This can make BMI less accurate for certain groups. Obesity Canada also notes that BMI should be interpreted carefully in certain populations, including older adults, very muscular individuals, and people who are extremely tall or short. In these cases, other health measurements and screenings can help provide a more complete picture.
The Canadian Obesity Guidelines make it clear that despite its limitations, BMI can still be a simple and useful screening tool. It may help identify people who could benefit from further evaluation or obesity management, but it should not be the only measurement used to assess someone’s health.
And for people already diagnosed with overweight or obesity, lowering BMI should not be the only goal. Instead, you and your healthcare provider can focus on understanding what may be contributing to weight gain, identifying barriers, making healthy lifestyle changes, and creating a treatment plan that works for you.
Diet & exercise are just one piece of the puzzle when it comes to reaching a healthier weight. For many people, psychological tools, medications, or surgery are the key for sustainable weight loss. Talking with a physician who specializes in weight management can help you get the treatments that are right for you… To find a doctor near you, click here.
This article was sponsored by Novo Nordisk Canada. All content is created independently by My Weight – What To Know with no influence from Novo Nordisk.
