More than 100 million Americans who qualify as overweight could see themselves tip into the obese category under newly introduced standards.

The traditional measure of overweight and obesity – body mass index (BMI) – may underestimate obesity-related risks in some people, according to the European Association for the Study of Obesity’s (EASO) framework.

The EASO’s guidelines don’t just consider BMI, but also waist-to-hip ratio, as well as all medical, psychological, and functional co-occurring issues. 

Relying solely on BMI leaves doctors blind to critical aspects of the ways and places where fat accumulates in the body and how that affects metabolism, and it fails to differentiate between muscle and fat.

A ‘good’ BMI can also mask underlying health conditions. Around a fifth of people within the normal weight category are unknowingly insulin resistant, meaning the body’s cells stop responding to the hormone that regulates blood sugar. It is a dangerous condition that can lead to diabetes.

Researchers from the American College of Physicians studied more than 44,000 adults of varying weight and health levels. 

Nearly 19 percent of those previously classified as ‘overweight’ by having a BMI of 25 to 29 were now considered ‘persons with obesity’ (PWO) under the European standard, which considers weight, waist circumference, and metabolic health markers like liver enzymes and insulin levels.

If the same shift were applied to all 110 million overweight Americans, roughly 20.7 million people would be misclassified as overweight when they’re actually obese.  

Relying solely on BMI leaves doctors blind to critical aspects of the ways and places where fat accumulates in the body and are increasingly considering people’s waist-to-hip ratios (stock)

‘Assessing obesity risk has become increasingly important as health payers consider approaches to ration effective but costly weight loss medications,’ researchers from the American College of Physicians said. 

Doctors in the US have been moving away from BMI as a reliable measure for obesity for years, opting instead to incorporate other factors and assessments, such as fat versus muscle measures, waist circumference, and metabolic health markers like liver enzymes and insulin levels.

Amy Woodman, registered dietitian and founder of Farmington Valley Nutrition and Wellness, told DailyMail.com: ‘As a dietitian with experience in both clinical and private practice, I have never relied solely on BMI, as it is only one small part of the overall clinical picture.

‘While I do consider BMI, I tend to give more consideration to a person’s eating patterns, physical activity, and comorbidities.’

BMI doesn’t account for where fat is stored in the body, which is crucial, the researchers behind the latest study concluded. 

A high waist-to-hip ratio, which reflects an apple body shape with belly fat, for instance, indicates that more dangerous visceral fat has accumulated around the abdominal organs, doubling or tripling the risk of heart attack.

A low ratio, however, creating a more pear-shaped figure, indicates that more fat is stored in the hips and thighs, and does not suggest a higher risk of heart attack or diabetes.

Dr Britta Reierson, a board-certified family physician and obesity medicine specialist at knownwell, told DailyMail.com: ‘There are numerous other factors that doctors must consider, including pre-existing health conditions, comorbidities, and body composition metrics such as muscle mass and excess adiposity. 

‘These metrics, along with others, help me and other doctors gain a clear picture of patients’ overall health.’ 

Based on BMI alone, just over 31 percent of individuals in the entire study population were considered normal weight, 33 percent were overweight, and 35 percent had obesity.

But under the new framework, more than half of the study population was defined as having obesity (54.2 percent). More men (about 22 percent) than women (about 16 percent) were newly classified as having obesity.

The new classification puts nearly one in five overweight adults at newly-recognized risk of certain obesity-related dangers from heart disease and diabetes to premature death. 

An estimated 40 percent of Americans are obese; a slight decrease from the 42 percent reported between 2017 and 2020. While the decrease is not statistically significant, it suggests obesity rates may at least be plateauing. 

The most common health condition among newly classified obese people was high blood pressure, at 80 percent. Arthritis affected 33 percent of them, diabetes just under 16 percent, and 10.5 percent had heart disease.

Overweight people by the European standards had a 46 percent lower risk of death than normal weight people, likely because BMI fails to distinguish muscle from fat or identify people who are metabolically healthy. 

The most dangerous type of fat is known as visceral fat, a firm internal layer that forms between the organs inside the abdomen. Subcutaneous fat, on the other hand, is the wobbly type of fat that lies just under the skin and causes cellulite to form

In the study, newly classified obese people did not have a higher risk of death compared to all normal-weight people, including those with chronic diseases. 

But when comparing people newly classified as obese to healthy normal weight people without any underlying health conditions, the former had a 50 percent higher risk of death, still lower than BMI-defined obese adults having an 82 percent higher risk. 

The study focused on upgrading individuals from overweight to obese status, but the European criteria could theoretically be used to downgrade some BMI-classified obese people, as well. 

A person with a BMI of 30 may count as obese but have a high amount of muscle compared to fat, a small waist-to-hip ratio, and zero comorbidities. 

Researchers suggest the similar mortality risk between newly classified obese and normal-weight individuals may stem from unaccounted comorbidities in the EASO criteria, where underlying illnesses causing weight loss could artificially elevate death rates in this group.

‘Some persons may have experienced unintentional weight loss due to undiagnosed conditions, such as gastrointestinal disorders, hyperthyroidism, or neurologic diseases, which can increase the risk for death,’ the researchers said.

There has been a global push to move beyond BMI as the sole determinant of health.

Dr Michael Aziz, an internal medicine physician and author of The Ageless Revolution, told DailyMail.com: ‘Recent research indicates that waist-to-hip ratio is more accurate in determining health outcomes.

‘The limitation of the BMI is that it does not distinguish between muscle and fat, so a very muscular individual may have less fat and more muscle and come up with a high BMI, while a sedentary person with a healthy BMI can have much more fat and less muscle.’

The above graph shows findings from a new CDC report, which states that obesity rates have fallen for the first time ever, though they still remain higher than 2013-2014

The study focused on upgrading individuals from overweight to obese status, but the European criteria could theoretically be used to downgrade some BMI-classified obese people, as well

A global group of experts, behind a report published earlier this year in the Lancet Diabetes & Endocrinology journal, formally proposed that BMI should not be used alone to determine a healthy weight, emphasizing the need for additional measurements.

Dr Reierson added that wider acceptance in doctors’ offices of the European standards is ‘a step in the right direction, as it starts to account for a range of other body composition metrics, secondary and related health conditions, and beyond the scale health metrics.’

She added: ‘Although BMI offers a glimpse into a patient’s metabolic health, it can’t be the end-all be-all.’