BMI is a Weak Tool to Measure Obesity and Health Consequences for 1 in 5 Americans

BMI May be All Wrong

We’ve had it all pound into our heads that fat is bad and lean is good.  Obesity is linked to heart disease, diabetes, hypertension, cancer, and a host of other health problems.  The Body Mass Index (BMI) is touted as the best method of determining whether someone is at the right weight or at risk for health problems because of overweight status.  However, a new study suggests that the BMI may not be the best indicator of whether someone is at a good weight for them.  In fact, for 1 in 5 Americans the BMI may be telling the wrong story.

The History of the BMI

The BMI was originally developed by a Belgian scientist, Adolphe Quetelet, in 1832 to define the “normal man” in terms of a host of different factors including arm strength and the age at which he first marries.  Ironically, Quetelet’s project had very little to do with obesity or obesity-related diseases.  He developed the equation to measure BMI–the ratio of height to weight in the average adult–using data collected from several hundred Belgian men.  His equation had very little impact on the medical community until long after his death, and did not take strong hold until the first large-scale studies were conducted on the effects of obesity in the early 20th century.  Since that time, health insurers have taken up the BMI as the quickest and easiest method of determining the proper weight for men and women and their risk of developing obesity-related health problems.

New Research Shows BMI is Faulty Measure

Now new research from two University of Pennsylvania physicians and obesity researchers shows that the BMI may be the quickest, easiest, and cheapest way to measure obesity but it isn’t the most accurate.  In fact, although many Americans are affected by metabolic disorder because of their overweight or obese status, evidence suggests that 10% of the population with BMIs over 30 are metabolically healthy.  Although that might sound like much, it translates into 24 million Americans who are constantly harassed by employers, public health officials, insurance companies and their healthcare providers to lose weight or pay the consequences (usually economic).  The researchers say that doctors especially should be careful about inferring to much from BMI that it is a perfect measure of who will die early and who will live long based on their body fat.  Specifically, the researchers say that people may carry excess weight for a variety of reasons including genetic, behavioral, psychological and social reasons and there is also a growing body of evidence to suggest that where fat is located on the body makes a difference to health (e.g. fat around the abdomen seems to be particularly problematic, whereas arm fat is not).  They suggest that doctors begin to utilize tools that may be more expensive and time-consuming, but that will provide an accurate picture of a person’s health trajectory.  For instance, tools such as body composition, adipose hormones, myokines, cytokines and other biomarkers would allow physicians to determine the fat-but-fit population from the skinny-but-unhealthy and the fat-and-unhealthy groups.