Should we ditch the Body Mass Index (BMI) as a measure of health? Today, it is the standard unit of measurement used to assess a person’s health via certain assumptions about overweight and obesity. Adopted in the 80′s by the health industry in America, BMI is simple to calculate – divide your weight in kilograms by the square of your height in meters. A 6 foot tall person (1.83m), weighing 200 pounds (90kg) would have a BMI of 27.
A BMI of 18-25 is considered normal
A BMI of 25-30 is considered overweight
A BMI of 30 and up is considered obese.
Your BMI is important because appears in various health records and has a direct effect on health insurance payments. The Equal Employment Opportunity Commission is proposing a rule that will allow employers to charge their employees up to 30% of their healthcare costs if their BMI is not in the normal range. The problem with BMI is that it is not a good indicator of health. In fact, a recent study has found that up to 74 million Americans are being wrongly classified unhealthy or healthy, simply because BMI is a poor indicator of health. According to the study:
34.4 million people with an “overweight” BMI are healthy according to cardiometabolic criteria (blood pressure, triglyceride and cholesterol level, blood glucose and insulin resistance, and C-reactive protein)
2 million people classified as extremely obese, with a BMI over 35, were also considered healthy by this measure
21 million people whose BMI is in the normal range, are actually unhealthy based on their cardiometabolic criteria.
If BMI is such a bad measure, why is it being used by everyone? Simply because there is no easy alternative to measure and calculate. All other measurements such as waist circumference and body fat are a bit more difficult to perform and translate into a meaningful score. It’s very easy and polite for doctors and nurses to measure height and weight. They don’t need to wrap their hands around you, as in, for example, a waistline circumference check. Body fat is harder to measure because the device used for measurement is substantially more expensive than a weight scale.
Another drawback of BMI is that it does not take into account the body shape of different people.
Some people have big frames; others may be stocky. These body types end up obese more than others, even though they are no less healthy. Athletes and muscular people are also punished by the BMI, because muscles weigh more than body fat. However, as it pertains to health risks, abdominal obesity is likely a better indicator than BMI. A report by the Center for Disease Control and Prevention has found an alarming increase in the waistlines of Americans. In just 12 years, the average waist size in the US grew from 36 inches to 38 inches for women and from 39 inches to 40 inches for men. During the same time frame, BMI levels barely changed.
What’s the practical application for you?
For one thing, you may not need to lose as much weight as you previously thought. Second, get a tape measure and start tracking your waist circumference. This is how to do it: 1. Place a tape measure around your bare abdomen just above your hip bone. 2. Be sure that the tape is snug, but does not compress your skin, and is parallel to the floor. 3. Relax, exhale, and measure your waist.
Sources: 1. Ford – Trends in Mean Waist Circumference and Abdominal Obesity Among U.S. Adults 1999-2012, JAMA, 2014 2. Tomiyama et al – Weight and cardiometabolic health: new perspectives– International Journal of Obesity, 2016
KISS Fact: Remember being thin is a true testament to health, I know a lot of sick skinny people. Another key point is these principles apply to the entire family. Healthy kids turn into healthy adults!