At your last physical, your doctor may have recorded your body mass index (BMI). That statistic has long been thought of as an indicator of how healthy someone is. While it's still helpful, the truth is a little more complicated, doctors say.
"It's not the only factor we look at, nor is it the best way to tell if patients are at a healthy weight," says Dr. Jennifer Brull, president of the American Academy of Family Physicians. "There are some people whose BMIs may not be a good reflection of how much body fat they have."
Here's what to know about different levels of BMI and what that actually means for your health.
BMI is calculated using a person's weight and height, with the idea that it can show if a person's weight is healthy based on an estimation of their body fat percentage.
Per the Centers for Disease Control and Prevention (CDC), these are the BMI categories for adults 20 and older:
One issue with this sort of calculation is that BMI can't actually distinguish between fat, muscle and bone mass, according to the CDC.
"A BMI that is low could mean a person doesn't have enough body fat. A high BMI could mean that they have too much body fat," Brull says, though she notes that "every body is different and BMI isn't one-size-fits-all."
While many doctors do consider BMI, Brull notes that it's a small portion of the conversation rather than the end-all-be-all. It's also important to consider factors such as the patient's diet, physical activity level, their relationship with food and wellness and even their socioeconomic status.
"This includes where they live, income, access to nutritious meals and grocery stores that carry fresh foods, transportation access and health literacy," Brull says. "BMI should be used as a screening tool and as a starting point for a conversation with a family doctor about weight."
Take athletes for example. Dwayne "The Rock" Johnson has made headlines in the past for being technically obese by BMI standards at 6 feet, 5 inches and around 265 pounds, despite the fact that he has a super-muscular build and regularly works out. Older adults can also be an exception: They tend to lose muscle mass and therefore could have a higher percentage of body fat, according to the AAFP.
"We know that muscle weighs more than fat, so their weight may not be a good indicator of how much fat they have in their body," Brull says. "Patients who suffer from being overweight or obese can face stigma. Focusing too much on weight rather than taking a more holistic approach can be detrimental to the care of all patients. Addressing these health risks require a customized, sensitive approach from a family physician."