How Your Waistline May Be a Better Indicator of Heart Health Than BMI

For seemingly forever, we have gauged whether we were gaining weight by the tightness of our pants’ waistband and by readings on a scale. Fortunately, we also have the more standardized Body Mass Index (BMI)—the measure for assessing health based on weight and height in a medical setting. Indeed, it is the primary eligibility measure for bariatric surgery.

Despite the popularity and widespread use of BMI, recent studies suggest that waist circumference is a better indicator of overall health. But before you rush out to buy a fabric tape measure, BMI still has benefits, even if it comes in second.

History of BMI

In the early 19th century, a Belgian mathematician named Adolphe Quetelet developed the BMI, also known as the Quetelet Index. It was a relatively simple formula that used one’s weight in kilograms divided by one’s height in square meters. Physicians could quickly categorize their patients based on this simple yet arbitrary calculation.

In the 1970s, Ancel Keys, an American physiologist, decided that BMI was a great way to identify obesity in populations around the world, and ever since, BMI has been widely adopted by health organizations, including the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC). It’s a remarkably straightforward method to assess whether individuals are underweight, average weight, overweight, or obese, but it has limitations when determining an individual’s weight. The system fails to account for potential considerations:

• Everyone is different. Yes, being so-called ‘large-boned’ is a thing. Some people are physically larger than others, and the BMI fails to consider that.
• Gender Differences: BMI does not differentiate between males and females, yet men and women typically have different body compositions. Men have more muscle and less body fat than women. A man and woman with the same BMI might have very different health profiles. For example, a man with a BMI of 27 could be very muscular and healthy, while a woman with the same BMI might have a high body fat percentage and be at greater risk for health issues.
• Muscle Mass: Athletes and individuals with high muscle mass often have elevated BMIs despite having low body fat and excellent health. Muscles weigh more than fat, so highly muscular people may be categorized as overweight or obese by BMI standards even though they have a low body fat percentage. So, if a physician reads the BMI without seeing the patient’s body to know musculature, they might make an incorrect assumption about the individual’s health and fitness.
• Body Frame: People with different body frames—small, medium, or large—can have vastly different BMIs despite having similar body compositions. BMI does not take into consideration the size and density of your bones. You’ll weigh more if you have a large frame with large bones.
  Body fat is not factored into the BMI equation, so its accuracy is skewed. People with a higher level of body fat are at risk for developing type 2 diabetes, high blood pressure, or cardiovascular issues.
• Age: As you age, your body composition and bone density change. Seniors have less muscle mass, and their muscles are often replaced with fat. As such, an older adult with a normal BMI may have high body fat because they have lost muscle from aging.

Waistline as a Health Indicator

In recent years, and considering reputable studies, healthcare professionals have noticed the limitations of BMI and have started to advocate for waist circumference as an accurate measurement of health.

Waist circumference provides insight into how much visceral fat you have and is a critical predictor of your heart health. Research has shown that a larger waistline is strongly associated with an increased risk of cardiovascular diseases, even in individuals with a normal BMI. This is because visceral fat is more likely to cause metabolic disturbances that lead to heart disease.

To determine your waist circumference, you’ll need a flexible cloth tape measure. Place the tape around your abdomen (remember to remove your clothing). Pull the tape measure right above your hip bone so it’s snug but does not compress your skin. Breathe normally and read what the measurement says as you exhale.

Waist circumference may be a far better predictor of health risks than BMI. Studies have shown that individuals with larger waistlines are more likely to develop cardiovascular diseases and metabolic disorders, even if their BMI is within the normal range. Waist circumference provides a clearer picture of your fat distribution and associated health risks.

The CDC suggests a waist circumference of more than 40 inches for men and 35 inches for women indicates a higher risk of health problems.

Visceral Fat vs. Subcutaneous Fat

There are two main types of fat in the body: Subcutaneous fat is right under the skin, and visceral fat is around the internal organs. Visceral fat is more dangerous than subcutaneous fat as it is metabolically active and causes widespread inflammation and insulin resistance. High levels of visceral fat are associated with increased risks of heart disease, type 2 diabetes, and certain cancers.

Waist-to-Hip Ratio

Another helpful measure is the waist-to-hip ratio, which compares the circumference of your waist to that of your hips. To calculate the waist-to-hip ratio, divide your waist and hip measurements. A higher ratio suggests more abdominal fat. According to the WHO, a waist-to-hip ratio above 0.90 for men and 0.85 for women is associated with a greater risk of heart disease and other health conditions.

The Bottom Line

BMI will continue to be a valuable tool for assessing health at a population level. However, when determining individual health, BMI takes a back seat. Factors such as gender, muscle mass, body frame, and age skew BMI results, making it an imperfect health measure.

Waist circumference, on the other hand, provides a more accurate assessment of visceral fat and associated health risks. By focusing on abdominal fat, waist circumference offers better risk prediction, simplicity, and a clear target for health improvement efforts. Waist circumference is also a crucial predictor of heart health, providing a more reliable measure for preventing cardiovascular diseases.

You can take a proactive approach to staying healthy by measuring your waistline as part of your post-operative bariatric health improvement plan.