According to the Center for Disease Control and Prevention, Body Mass Index (BMI) is an inaccurate measure of health for about 1 in 5 people. This finding comes from a landmark study released in 2008 in The Journal of American Medical Association: Internal Medicine. Data for 5440 individuals was collected over a period of five years (1999-2004) from the National Health and Nutrition Examination Surveys. The researchers studied many factors, in addition to height and weight, including blood pressure, “good” cholesterol, triglycerides, blood sugar and the c-reactive protein — a marker for inflammation. All of these factors are indicators of cardiovascular health.
The research showed that people with normal BMI’s were on average, healthier than people with high BMI’s, as expected. The study, however, also showed that having a normal BMI did not guarantee good cardiovascular health and having an above normal BMI did not guarantee poor cardiovascular health. In fact, almost 24 percent of “thin” adults, which amounts to more than 16 million American people, had at least two of the risk factors described above. More surprisingly, a little less than half of the individuals who were categorized as overweight or obese by BMI calculations were metabolically healthy.
New research and discussion amongst nutritionists and scientists suggests that the clearest indicator of health isn’t weight, but body fat. The ambiguity of BMI is in the definition itself: the ratio of weight in kilograms to height in meters squared. The concept of weight can often be misleading because weight does not just include body fat, but also includes muscle mass and bone structure. According to BMI, a person that has large muscle mass and little fat could be overweight and individuals with little muscle mass and more fat could be underweight or normal weight. In fact, the concept of BMI is so limited that according to BMI measurements taken in 2005, almost half of all NBA players fell in the “overweight” category.
Muscle and bone structure, however, are not the only problems with using BMI as a measure of health. Many individuals with high BMI’s are not extremely muscular, yet are still healthy. People with normal “BMI’s” may be toned, but are still unhealthy. Another reason that BMI can be misleading is that it does not take into account the type of fat that the person has. Visceral fat or “deep” fat is different from subcutaneous fat because visceral fat covers the organs in your body whereas subcutaneous fat is found underneath the surface of the skin. Individuals with larger stomachs or waists tend to have high amounts of visceral fat, which can cause metabolic problems and increase the chance of getting diabetes, heart disease, stroke and even dementia.
It is clear that the amount of fat and the type of fat are both crucial factors in measuring overall health. BMI is flawed because it doesn’t measure either. So, rather than being concerned about the number on the weighing scale, it might be a better to measure waist size using a measuring tape. Waist size and BMI aside however, it is smart to just focus on eating healthy and exercising regularly. The combination of good food and exercise will stave off fat, specifically visceral fat.
Sabrina Leung ‘18 is the Digital Editor majoring in International Relations-Political Science with a minor in History. She is best reached at firstname.lastname@example.org or @sabrinatzleung on Twitter.