DEAR MAYO CLINIC: At a recent appointment, my blood pressure and cholesterol were normal, but my doctor mentioned that my BMI is at an unhealthy number (28). Does this mean I need to lose weight even though I have no health problems?
ANSWER: Although weight is an important measure of health, it's not the only thing to consider when assessing overall health. Other factors play a role as well, such as how active you are and the amount of muscle versus fat you have in your body. Taken together, these variables can help give you a more comprehensive view of your health, now and into the future.
Health care providers often assess the effect of a person's weight on their health using a calculation called the body mass index, or BMI. It is calculated by dividing your weight in kilograms by your height in meters squared. You can find your BMI by going to mayoclinic.org and entering your height, weight and waist size into the online BMI calculator.
BMI values between 18.5 and 24.9 are considered normal. Values between 25 and 30 are considered overweight, and values greater than 30 are considered obese. Generally, a BMI that is more than 30 is associated with higher risks to health. These risks include a higher likelihood of developing diseases and health problems, such as heart disease, diabetes and high blood pressure.
That said, BMI does not always provide the full story regarding health risks for some people. That is because it does not take into consideration individual factors, such as bone or muscle mass. For example, if you lead an active lifestyle and regularly participate in both aerobic exercise and weight training activities, you may have a healthy percentage of body fat despite having a BMI above the normal range. So in that situation, a higher BMI does not necessarily translate to higher health risks. It is important to note, though, that this situation is less likely when BMI values are higher than 35. Beyond that point, additional weight is much more likely to be distributed as fat and not muscle.
In addition, people of Asian descent may have an increased risk of health problems at a lower BMI threshold than the general population.
It is also possible to have a normal BMI while your body fat percentage is high enough to increase health risks. People with this condition, known as normal weight obesity, may have the same serious health risks as someone who is obese. This is especially true for individuals who have a high percentage of body fat around the waist. Research has shown that people who carry a high proportion of body fat at the waist have increased health risks.
To get the most accurate assessment of your health, first find your BMI. Then take a look at your lifestyle. If your BMI is less than 35 and you exercise regularly — participating in at least 150 minutes of physical activity each week — you may not be at an increased health risk. If your BMI is 30 or higher, and you do not have an active lifestyle, your health may be at risk. If so, talk to your health care provider about changes you can make to improve your health now, as well as lower your risk for health problems in the future. — Dr. Maria Collazo-Clavell, Endocrinology, Mayo Clinic, Rochester, Minnesota