Why Is BMI Important?

Written by Melodie Anne ; Updated December 07, 2018
Why Is BMI Important?

Why Is BMI Important?

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The body mass index, or BMI, is a calculation used to determine your level of body fat. In some cases, it can help a doctor determine your overall fitness and your risk of developing chronic diseases. Still, BMI is not the only factor your doctor considers, and it isn’t a completely reliable assessment for every body type.

What BMI Results Mean

Generally, if you’re at a healthy weight, your body mass index should fall between 18.5 and 24.9, notes the National Heart, Lung and Blood Institute. If your BMI is below 18.5, you could be underweight. On the other hand, a BMI greater than 25.0 is categorized as overweight, while a score above 30 is considered obese.

Why The Number Is Important

A body mass index in the low range signals that you could be malnourished. Maybe your body isn’t properly absorbing nutrients or maybe you’re just not getting enough calories to support your activity level. Conversely, having a BMI on the higher end alerts your physician that your risks of heart disease, diabetes and certain cancers are higher than someone with a normal BMI. Your doctor might set you up with a registered dietitian, who can help you get your weight back on track and reduce your risk of developing health problems.


While BMI is a starting point to evaluate your health, it isn’t flawless. For example, it doesn’t account for gender, and women tend to have more body fat than men. So as a woman, even if your body mass index is in the normal range, you could still have a high percentage of body fat. The calculation also doesn’t account for muscle mass. Muscle weighs more than fat, so if you lift weights and have toned muscles, your BMI could be high even if you’re not overweight. The test also doesn't account for genetic factors, bone density or your activity level, or take into consideration the fact that thinness doesn't necessarily equal healthiness.

Better Measurements of Health

Given the frequent unreliability of BMI tests, you may want to use other tools to assess your wellness and body fat levels. Important signs of wellness include positive energy levels, normal digestion, eating a variety of nutritious foods each day and not feeling famished or overly "stuffed" throughout the day. Some fitness experts use skin calipers to measure body fat, which can be more accurate than BMI tests. You can also judge weight loss by clothing fit or using a tape measure on occasion to measure your waist circumference.

About the Author

Melodie Anne


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