Is Your BMI Really Giving You The Full Picture Of Your Health?

Up until recently, someone's BMI, or body mass index, was widely regarded as the best standard of measurement for gauging their overall level of health. Taking into consideration just two factors -– height and weight –- BMI has been used as a standard by which to judge a person's overall health in various settings, from doctor's offices to schools in physical education and health classes for decades.

According to the CDC, you are considered to be of normal weight if your BMI is between 18.5 and 25, whereas you are considered overweight if your BMI measures between 25 and 30. Any BMI under 18.5 is considered underweight, while a BMI of over 30 is considered obese. Pretty simple, right? Maybe not.

Many medical professionals and other health experts now argue that because of BMI's one-size-fits-all approach, it shouldn't be the gold standard by which to judge whether or not someone is healthy, as health is based on the individual and is influenced by other factors in addition to obesity. "Excess weight can be a contributing factor to common diseases, but it is only one piece of the puzzle," registered dietitian Suzanne Kalmbach, MA, RDN, tells Byrdie.

While BMI can be looked at as a tool to get a better understanding of certain aspects of one's health, it falls short in a lot of areas. Understanding the context in which to interpret your BMI is essential in understanding what it's good at -– and what it's not.

BMI doesn't consider muscle mass

While someone's BMI is measured by taking into account their height and weight, many experts say that the standard of measurement falls short in its inability to factor in muscle mass. "BMI isn't an accurate representation of health because it takes the ratio of height and weight and doesn't factor into account the type of weight a person may have, such as muscle compared to fat," says exercise physiologist and sports medicine chiropractor Tom Kearn, DC, ICCSP, via Byrdie. By this standard, someone who is athletic and exercises a lot could have a lot of muscle and very little body fat but still be classified as "overweight" and, therefore, unhealthy.

On the contrary, having a healthy amount of muscle mass has been shown to actually improve your overall health. Muscle mass naturally diminishes over time, which is why many older adults have a hard time with physical activities like walking or climbing stairs. According to Medical News Today, maintaining a healthy muscle mass can help slow muscle mass loss over time and help you stay mobile and active longer.

Thin doesn't always mean healthy

Thinness is also not always an indication that someone is healthy. According to ABC News, a 2010 study found that an estimated 30 million Americans have what is considered "normal weight obesity" or are considered to be "skinny fat." According to Healthline, "skinny fat" refers to someone having a BMI that is considered to be "normal" or healthy on paper but have a high amount of body fat with very little muscle mass.

People with this amount of body fat and muscle mass face a higher risk of diabetes and heart disease –- meaning someone who looks skinny but has a poor diet and does not exercise could be far more at risk for obesity-related health issues like heart disease and diabetes than someone who is overweight by BMI standards but regularly exercises and eats healthy. "We would regularly see people who had heart attacks come to [our] rehab program and look perfectly fine," Carol Garber, a professor of Movement Science at the Teacher College at Columbia University, said via ABC News. "If you measured their body fat, they had a greater proportion of fat than they would have thought."

BMI and eating disorders

In addition to not providing a full picture of health, adolescent exposure to BMI screenings can lead to an obsession with weight. In fact, a recent study found that BMI screenings in school health or physical education classes increase the risk of adolescent weight insecurity and disordered eating. The study found that the use of BMI in school settings can increase the stigmatization regarding weight for adolescents, which can lead to bullying and teasing based on weight –- particularly for those with a higher BMI. The study also concluded that exposure to BMI screenings in schools has been shown to be a factor in eating disorder development in adolescents.

The idea that thinness equals healthiness also often leads to people being denied access to eating disorder treatment due to their BMI not being "low" enough for them to classify as having an eating disorder. Certain eating disorders, like binge eating, do not cause a lowered BMI. Because of this, someone with an eating disorder but a BMI that isn't considered to be underweight can often go untreated -– which is particularly alarming given that binge-eating disorder is over three times more common than anorexia and bulimia combined (per Byrdie). "People can become obsessed with their BMI category, leading some to get caught up in quick-fix weight-loss fad diets and not focusing on their overall health," Kalmbach says (via Byrdie).

If you need help with an eating disorder, or know someone who is, help is available. Visit the National Eating Disorders Association website or contact NEDA's Live Helpline at 1-800-931-2237. You can also receive 24/7 Crisis Support via text (send NEDA to 741-741).