The Body Mass Index (BMI) is a measure of body fat content in individuals. Calculated by dividing one’s weight in kilograms by the square of one’s height in meters, it has been used as a measure of a person’s weight and health in doctors’ offices and statisticians since the 1970s.
However, researchers have long highlighted how in failing to account for muscle mass, bone density, overall body composition, racial and sex differences, the BMI is largely inaccurate and misleading.
The BMI, which was created in the 19th century by Belgian statistician Lambert Adolphe Jacques Quetelet, was never intended to indicate the level of body fat content in individuals. Rather, the formula was produced to create a quick and convenient way to measure the degree of obesity in a large population of people to assist the government in allocating resources. However, the ease of the formula meant that doctors and insurance companies replaced more complex measures of measuring body fat, and so it became the norm.
According to the BMI, you are a normal weight if your BMI is between 18.5 and 25, overweight if it is between 25 and 30, and anybody with a BMI of 30 or more is deemed obese.
BMI only factors in weight and height to its formula, and therefore other parts of the body which influence body weight are not taken into account. For example, somebody who is very muscular, such as an athlete, but has very little body fat could be considered obese, according to the BMI.
Muscle weighs more than fat, and therefore BMI would equate the lifestyles and weight category of an Olympic sprinter with a sedentary person with an unhealthy lifestyle. By not making a distinction between muscle, fat, bone and excess water weight, the BMI cannot accurately measure a person’s level of fat or fitness.
Additionally, BMI is not reliable to use on elderly adults, who have generally lost some amount of muscle and bone mass. In this way, an elderly person’s BMI could be within a normal range when they may actually be overweight.
A person whose BMI deems them overweight are generally automatically classed as unhealthy, yet an article published in Scientific America found that 54 million Americans had been classed as overweight, but when they undertook other cardiometabolic measures such as blood pressure, blood sugar and cholesterol, their results showed that they were perfectly healthy.
Despite this, authorities such as the Centre for Disease Control and Prevention (CDC) and the National Institute of Health (NIH) in America still promote BMI as a reliable indicator of body fatness.
Regardless of the contention surrounding the BMI, obesity is still a considerable health problem that poses severe repercussions in people’s overall health and wellbeing.
The best way to maintain a healthy lifestyle and prevent obesity in adults has nothing to do with measuring height against weight.
Consuming less processed food and saturated fats, engaging in regular exercise, eating plenty of fruits, vegetables and foods high in dietary fibre are all important in maintaining a healthy lifestyle.