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One third of normal-weight individuals are actually obese, study finds

[July 20, 2023: Staff Writer, The Brighter Side of News]

New research has dramatically altered our understanding of the measurements determining health risks associated with obesity. (CREDIT: Creative Commons)

Recent scientific research from Tel Aviv University's School of Public Health, Faculty of Medicine, has dramatically altered our understanding of the measurements determining health risks associated with obesity.

A team of esteemed researchers and academics, including Prof. Yftach Gepner, PhD student Yair Lahav, and their collaborator Aviv Kfir, has presented compelling evidence to suggest that Body Mass Index (BMI), a commonly used parameter to assess individual's health, may be a less accurate indicator of health risk compared to body fat percentage.


The research highlights the critical importance of "anthropometric" data, the scientific term referring to the measurements and proportions of the human body, in deciphering the intricate relationship between body composition and health risks. After careful examination of anthropometric data from approximately 3,000 Israeli women and men, the research team has concluded that body fat percentage offers a more reliable reflection of an individual's overall health and cardiometabolic risk.

"Israel is a leader in childhood obesity and more than 60% of the country's adults are defined as overweight," says Prof. Gepner. He goes on to elaborate that while BMI is considered a standard health indicator, the paradox lies in the understanding of obesity itself.


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"The actual measure for obesity is the body's fat content, with the maximum normal values set at 25% for males and 35% for females. Higher fat content is defined as obesity and can cause a range of potentially life-threatening cardiometabolic diseases," Prof. Gepner explains.

The striking difference between these two measurements, BMI and body fat percentage, has led to a phenomenon termed 'the paradox of obesity with normal weight'. It implies a higher than normal body fat percentage in individuals who are considered to have a 'normal weight' according to BMI.

This paradox forms a cornerstone of the extensive research undertaken by Prof. Gepner and his team. Their research, notably the largest of its kind conducted in Israel, sought to unravel the prevalence of this 'paradox' in Israel's adult population.


"Obesity with normal weight is much more common in Israel than we had assumed," warns Prof. Gepner. This fact unravels a glaring blindspot in the current BMI-driven health system, wherein people of 'normal' weight but high body fat percentage can be left untreated and unguided, putting them at a heightened risk for various cardiometabolic diseases.

In the extensive investigation, the researchers leveraged a range of tools to gain a comprehensive understanding of participants' body composition. They used BMI scores, DXA scans (a technique that utilizes X-rays to measure body composition, including fat content), and analyzed cardiometabolic blood markers.

Associations between body fat and age among the entire study population across gender, n = 3,001. (CREDIT: Frontiers in Nutrition)

The analysis revealed that 38.5% of the 'normal weight' women and 26.5% of the 'normal weight' men were categorized as 'obese with normal weight', meaning they had excessive fat content despite their normal weight as per BMI. Further analysis unveiled a significant correlation between 'obesity with normal weight' and high levels of sugar, fat, and cholesterol.


These are major risk factors for cardiometabolic diseases, highlighting the imperativeness of identifying and treating this hidden population. In an intriguing finding, 30% of the men and 10% of the women deemed 'overweight' had a normal body fat percentage, underscoring the pitfalls of relying solely on BMI.

In response to these illuminating findings, the research team strongly recommends the adoption of body fat percentage as the benchmark for assessing health risks and obesity. Prof. Gepner insists on equipping clinics globally with devices capable of accurately measuring body fat content.

The non-linear association between BMI and fat mass; n = 3,001. (CREDIT: Frontiers in Nutrition)

This would require widespread adoption of tools such as skinfold calipers to estimate body fat based on the thickness of the subcutaneous fat layer and bioelectrical impedance analyzers, devices already in use at many fitness centers, that gauge body composition based on the body's electrical conductivity.


"Our study found that obesity with normal weight is very common in Israel, much more than we had previously assumed, and that it is significantly correlated with substantial health risks," warns Prof. Gepner. He further emphasizes the urgent need to pivot from the prevailing reliance on BMI to a more holistic understanding of body composition, especially body fat percentage.

The association between body fat and elevated abdominal circumference among the normal BMI group by gender; n = 967. BF% in this group was strongly correlated with abdominal circumference for men (r = 0.61, p < 0.001) and women (r = 0.63, p < 0.001). (CREDIT: Frontiers in Nutrition)

Prof. Gepner envisions that, "equipping all clinics with suitable devices for measuring body fat content, and gradually turning it into the gold standard both in Israel and worldwide," will lead to a more precise diagnosis of obesity, resulting in more effective prevention of disease and early mortality.

This groundbreaking study from Tel Aviv University, published in the reputed journal Frontiers in Nutrition, indeed prompts a much-needed rethinking of our current strategies in managing obesity and related health risks. By illuminating the limitations of BMI as a standalone measure of health, it underlines the importance of embracing body fat percentage as a more precise and reliable health indicator.


This transformative research from the School of Public Health at Tel Aviv University's Faculty of Medicine opens up new horizons for obesity research and public health policy. The study's profound implications could well revolutionize obesity management, shifting the focus from weight alone to a more comprehensive understanding of body composition, thereby ensuring a healthier future for all.

For more science news stories check out our New Discoveries section at The Brighter Side of News.


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