Body mass index (BMI) is a measure of your weight relative to your height.
For all men and women 20 years old and older, the BMI measurement is classified into one of four main weight categories:
People of Asian descent may have greater health risks at a lower BMI. People in this group may be placed in the overweight range if their BMI is between 23 and 25 and may have obesity if their BMI is 25 or greater.
BMI is a screening tool that can let you know if you may be at risk for weight-related health problems. But because it doesnât directly measure fat, there are some important things it canât take into account :
Where your body fat is located: Maybe the most important thing that a BMI measurement canât tell is where youâre storing fat in your body. Subcutaneous fat is just under your skin â itâs the fat you can see. But visceral (or abdominal) fat settles around your organs and has the greatest impact on your health. A high amount of this type of fat raises your risk for diabetes, heart disease, certain cancers, and other serious health problems.
Age: Body fat as a percentage of total body weight begins to go up around age 30.
Sex: At the same BMI, women (or people assigned female at birth) have about 10% more body fat than men (or people assigned male at birth).
Race/ethnic group: Different races or ethnic groups can have differences in body makeup at the same BMI. This includes such things as bone density, percentage of body fat, and overall body size.
Muscle mass: BMI is a measure of relative weight compared to height. It doesnât measure how much of your weight is made up of muscle. A person with more muscle tissue as a percentage of body weight can have the same BMI as someone with more body fat.
Pregnancy: You shouldnât use a BMI measurement to see if youâre at a healthy weight while youâre pregnant. Talk to your doctor about the weight range that is right for you at this time.
A BMI range tells you if youâre in a certain weight category. Compared to other tests your doctor can perform, itâs an effective measure of whether that weight category may increase your risk of certain serious health problems.
But taken alone, it doesnât mean that youâre âfatâ or âskinny.â It canât tell you if youâre healthy or not or diagnose you with any condition. Talk with your doctor about your weight and your BMI. They can help you understand it as part of the bigger picture of your health as an individual and make decisions that are right for you.