Body Mass Index: what you need to know

One of the metrics measured during a physical is your weight to determine your body mass index (BMI). You may have been disappointed to learn that your BMI fell into the “overweight” or “obese” category. Just what is BMI and why does it matter?

According to WebMD, BMI is a formula based on height and weight that is used to measure fatness. If you know your height and weight, the Mayo Clinic offers an online calculator to help you get a sense for your BMI.

Once you know your BMI, the Centers for Disease Control (CDC) uses the following guidelines:

BMI Weight Status

Below 18.5


18.5 to 24.9


25.0 to 29.9


30.0 and above


Because BMI is a simple formula and doesn’t take into account actual percentage of fat and muscle, it’s not exact and is often used as just one measure. For example, the CDC cites factors like age, race and sex as having an impact on the correlation between BMI and body fatness.

To get an accurate picture of health and risk for disease, a healthcare professional might recommend additional methods like skinfold thickness and waist circumference measurements. Using your BMI as a starting point, talk with your healthcare provider to determine if you need to gain or lose to achieve a healthy weight.

If you need to lose or maintain your current weight, the National Heart, Lung, and Blood Institute recommends:

  • Setting the right goals for weight loss—one to two pounds per week is generally considered reasonable and safe.
  • Balancing calories with physical activity—if you use more energy than consume calories, you’ll lose weight. There are lots of simple ways to cut calories like swapping soda for water or skipping mayo on your sandwich.
  • Developing a healthy eating plan—including a mix of nutrients, controlled portion sizes, and keeps an eye on calories. [link to new blog post]
  • Keeping physically active—at least 30 minutes of moderate activity each day. You might jumpstart your efforts by working with a personal trainer, and it’s a good idea to incorporate fitness into everyday activities like taking the stairs at work instead of hitching a ride on the elevator.