- Body Mass Index (BMI), or the calculation of your weight in kilograms divided by the square of height in meters, is one method of determining if someone is at a healthy weight.
- Measuring one’s BMI, however, is debated as many believe it’s not the most accurate means of measuring a person’s health.
- BMI doesn’t take into account factors such as age, ethnicity, and muscle mass.
Chances are, last time you visited your doctor, you had your height and weight measured and your BMI calculated. Depending on the numbers, you were likely classified in one of four categories: underweight (below 18.5), normal weight (between 18.5 and 25), overweight (between 25 and 30) or obese (30 or greater).
If your BMI is in a higher category, however, doesn’t necessarily mean you aren’t healthy.
BMI, or the calculation of your weight in kilograms divided by the square of height in meters, was created in 1832 by a mathematician to measure and follow populations trends of obesity. It wasn’t intended to be used for determining a healthy weight for an individual.
The formula doesn’t take important factors into consideration including family medical history, genetics, lifestyle, age, gender and muscle mass. Depending on many of those factors in your own life, you could be perfectly healthy even with a higher BMI.
Here are six reasons your BMI is higher than it should be, even if you’re perfectly healthy.
Just be sure to check with your doctor about your holistic health instead of relying on a single healthy indicator.
If you have a high muscle mass, your BMI is going to be higher.
As Business Insider’s Erin Brodwin explained in a post, BMI doesn’t account for body composition, including differentiating between muscle mass and fat.
Muscles are denser and heavier than body fat, so if you have high muscle mass, your BMI might indicate that you’re overweight or obese. BMI treats a person’s weight as one entity, instead of accounting for muscles, bone density and fat, which all make up a person’s weight.
Your height could make you seem “fatter” with BMI, if you’re tall
- Vivek Prakash/Reuters
BMI overexaggerates weight in tall people and underexaggerates weight in short people, according to Nick Trefethen, a professor of numerical analysis at the University of Oxford. The professor wrote a letter to The Economist in 2013 explaining that because BMI squares height, it makes tall people think they are fatter and short people think they are thinner.
Depending on your ethnicity, you could have a higher BMI and still be healthy.
Studies have shown that people of Asian descent have a greater risk of developing type 2 diabetes at a lower BMI, while African-Americans may have a higher BMI without health risks that go along with obesity.
Researcher and editor of the International Journal of Obesity, Richard L. Atkinson, MD, told WebMD that African Americans are less likely to have fat around their abdomen (which is indicative of greater health risks) and more muscle mass.
If you’re older, it might be healthier if you’re a bit heavier.
- Kevin Lamarque/Reuters
Though it is unclear why this is the case, Atkinson told WebMD that older people who are slightly overweight tend to live longer than leaner elderly people.
“People who are older probably should have a little more fat on them, [but] they shouldn’t have a BMI of 30,” he said.
Depending on where your body stores fat, you could be at less risk of disease even with a high BMI.
Not all fat is equal. The fat that builds up around your waist and belly is more dangerous to you, because that fat surrounds your organs, whereas the fat around your thighs and hips has less effect on whether you’ll develop diabetes or heart disease.
This is why measuring the circumference of your waist is a better determination of your health. If the circumference of your waist is below 35 inches as a woman and 40 inches as a man, you’re more likely to have a healthier weight.
“[BMI] also does not tell us the distribution of body fat in a person,” Eva Tseng, MD, MPH, an Assistant Professor of Medicine at Johns Hopkins, told PopSugar. “We know that people with more central or abdominal adiposity [obesity] have a higher risk of premature cardiovascular disease, diabetes, and death compared to people with a similar BMI but less abdominal adiposity.”
Even if you exercise more and eat better and have a healthier lifestyle, you may not lose any weight, so your BMI will stay the same.
Even if you start exercising and eating healthier, you might not lose weight. Though you’ll be losing fat, you will also be building muscle, which isn’t accounted for in BMI. So if your weight doesn’t change, neither will your BMI, despite the decrease in risks of heath disease, diabetes and death related to obesity.
According to a 2007 study done on veterans with type 2 diabetes, a person’s level of fitness predicts their mortality better than BMI. So if you are generally fit and active, you’re going to be healthier than someone who isn’t, regardless of their BMI.
Visit INSIDER’s homepage for more.