If you were asked to think of a few adjectives to describe actor Dwayne “The Rock” Johnson, “obese” would probably not be one of them. So not surprisingly, when Yahoo! Health released an article early last year stating that Johnson was in fact “technically obese,” it took the world by storm. How could a man in top shape, equipped with a personal trainer and a background in professional wrestling, possibly be obese? The explanation lies in a standardized measurement system familiar to many people—body mass index, more commonly known as BMI.

BMI involves a simple calculation that correlates an individual’s height (in meters) and weight (in kilograms) to determine relative proportions of body fat. Thus, medical professionals often employ BMI as a criterion for obesity. However, BMI has a notable pitfall in that it cannot distinguish between body fat and muscle mass, causing exceptionally built professionals like Johnson to be incorrectly categorized because of added muscle weight. And Johnson wasn’t the only one—according to the same Yahoo! article, his Fast & Furious costar Vin Diesel would also fall under the “overweight” BMI bracket.

BMI calculations are often used to determine if a person is overweight.

Image Source: Melissa Ross

In addition to misinterpreting muscle for fat, BMI does not specify between different types of fat stores and their associated locations, which can drastically affect an individual’s risk for metabolic conditions like heart disease. For example, unlike fat around the hips or thighs, belly fat tends to lead to greater consequences, such as increased bad cholesterol levels or high blood pressure. Furthermore, BMI must be interpreted differently for children, as their bodies are still changing over time; their continuous growth can make it difficult to determine whether a child’s weight at a given age or size is normal.

While BMI can be a helpful tool for promoting a healthy lifestyle, it is also important to remember that it is not the be-all and end-all of wellness. Every human body is different, so if you have specific questions or concerns about BMI, always speak to a medical professional rather than relying on potentially faulty virtual BMI calculators.

Feature Image Source: 60 by Fit Approach

Zareen Thakor

Author Zareen Thakor

Zareen is a Biology graduate of the University of California, Los Angeles. Aside from health and the life sciences, her passions include reading, creative writing, and traveling the world.

More posts by Zareen Thakor