Why BMI is failing us (and what to use instead)

Body Mass Index, or BMI, is a centuries‑old measure that has been under scrutiny for decades. Now a new 2026 study highlights its downfalls. In this article, we explore what BMI gets wrong, what modern health measures get right, and how to gain a clearer picture of your real cardiometabolic risk.

Read on and you’ll discover:

• Why BMI is a basic screening tool, not a diagnosis
• Why it matters to distinguish between muscle and different types of fat
• How simple measures like waist‑to‑height ratio can be more revealing
• What’s emerging as the next step beyond BMI
• Why BMI became so widely used in the first place

What is BMI, and why did it take off?

For anyone who might need a quick refresher, BMI stands for Body Mass Index. It’s a simple calculation based on height and weight, and it’s commonly used to categorize people as underweight, healthy weight, overweight, or obese.

It was way back in the 1800s when BMI first became a thing. Developed by Belgian mathematician and statistician Adolphe Quetelet, it was originally known as the Quetelet Index. And it wasn’t actually designed to assess individual weight or health. Its purpose was to study population trends and help governments understand patterns of weight across large groups.

BMI became a popular self-assessment because it’s quick, cheap, and easy to apply at scale. And while that simplicity has value, it’s also where the problems begin.

Where BMI falls short

BMI becomes unstuck because it only looks at total body weight. It doesn’t distinguish between fat, muscle, or bone. While this isn’t hugely problematic for analyzing the general population, for individuals, it can be misleading. Athletes and muscular people are a classic example. Many are labeled overweight or obese by BMI standards, despite having low levels of body fat and excellent health. At the other end of the spectrum, someone can fall within a ‘healthy’ BMI range while carrying unhealthy levels of fat.

BMI also tells us nothing about where fat is stored, and that matters. Two people can have the same BMI but very different health risks depending on the type and location of their fat.

As Bryce Hastings, Les Mills Head of Research, explains, not all fat is created equally. “Visceral fat is the most harmful kind. This is the fat stored deep around the organs. It’s far more dangerous than subcutaneous fat, the softer fat just under the skin that you can pinch.”

Measuring what actually matters

For Performance Physiologist Professor Paul Laursen, a key mantra is ‘understand what matters and then measure what matters’. He says the fact that body weight is made up of muscle mass, fat mass and bone mass, makes ‘weight’ largely irrelevant. On its own, total weight tells us very little. What matters far more for long‑term health is visceral fat, the deep fat linked to inflammation and metabolic disease.

What really predicts health risk

Hastings explains, visceral fat is one of the strongest predictors of cardiometabolic risk. It wraps around vital organs such as the liver, pancreas, and intestines and a specific form, known as epicardial fat, sits directly around the heart.

The nasty thing about visceral fat is that it actively interferes with normal body function. It drives inflammation, increases insulin resistance, and contributes to metabolic dysfunction. Over time, these changes raise the risk of serious conditions including heart disease and type 2 diabetes.

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The quick and easy check: simple waist to height

One of the easiest ways to estimate risk is with a tape measure. According to Laursen, waist‑to‑height ratio offers a practical snapshot of how much fat you carry around your middle, the area most strongly linked to heart and metabolic risk.

The method is simple. Measure your waist, double that number, and compare it to your height. If your waist measurement multiplied by two is greater than your height, there’s a good chance you fall into the ‘overfat’ category.

TRY THIS >> Measure your waist. Multiply it by two. If it’s larger than your height, it’s time to pay attention.

Laursen cautions this is still just an indicator. Dangerous visceral fat does not always show up as a larger waistline. Some people appear slim and healthy on the outside but carry hidden risk on the inside.

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Looking beyond a singular number

As awareness of BMI’s limitations grows, researchers and clinicians are turning to more comprehensive tools. One example is the Visceral Adiposity Index, a model that combines BMI, waist circumference, and blood markers to better estimate visceral fat function.

Advances in medical imaging and health screening are also helping build a more accurate picture of cardiometabolic health. These tools can identify people who appear healthy by BMI standards but carry unhealthy fat patterns, as well as those with higher BMIs who remain metabolically healthy.

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Why moving beyond BMI matters

It’s not just a matter of making muscular individuals feel better about their metrics. An overreliance on BMI has had real‑world consequences all across society. For years, BMI cutoffs have influenced access to medical screening, treatment, and even insurance approvals – affecting everything from knee surgeries to fertility treatment, bariatric procedures and more.

Today, there’s growing momentum toward more nuanced approaches. Many clinical frameworks now combine BMI with waist measurements and other markers to better identify risk, especially in people who would otherwise be overlooked.

The bottom line

BMI is a screening tool, not a diagnosis. Used in isolation, it can miss important details. Used alongside other measures, especially waist‑based assessments, it can still play a role in raising awareness.

Carrying excess visceral fat increases the risk of chronic inflammation, reduced quality of life, injury, and serious diseases such as cardiovascular disease, cancer, and dementia. The earlier this risk is identified, the greater the opportunity to take action.

Taking action: How to cut visceral fat

Contrary to persistent belief, we can’t target body fat with specific exercises. However, when it comes to reducing dangerous visceral fat, science shows turning to high‑intensity interval training can be a particularly effective approach. One published study shows that when exercisers added LES MILLS GRIT™ to a standard training routine, it took just 8 weeks to see significantly greater reductions in abdominal girth and visceral fat than with conventional gym training.

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Fat reduction isn’t the only way LES MILLS GRIT benefits your health. Watch this short video to see what happened when the Les Mills Lab teamed up with Dr. Jinger Gottschall to explore how LES MILLS GRIT can impact the fitness and body composition of fit and active adults. Read more about the benefits of LES MILLS GRIT .

As far as nutrition goes, there are no magic fat-reducing foods (again, despite what Insta says). Although there are some foods to avoid. Nutritional expert Niki Bezzant advises, “Cutting out ultra-processed foods will go a long way towards cutting overall body fat and by extension, the dangerous stuff that lurks around the organs. That means ditching the sugary foods and drinks, refined white carbohydrates, fatty and salty snacks. Replace them with whole, fresh foods (mostly plants) and you’ll be on the right track.”