New research to be presented at this year's European Congress on Obesity (ECO 2025, Malaga, Spain, 11-14 May) shows that the internationally recognised body mass index (BMI) cut-off points greatly overestimate overweight and obesity in male athletes. The study, from Italy, also proposes new cut-off points for overweight and obesity in this group.
Body mass index (BMI) is a key method for measuring people's weight status, defining whether they have normal weight, overweight or obesity. It is easily calculated by dividing an individual's weight in kilograms by the square of their height in metres. A BMI of 25 kg/m2 or above is in indicator of overweight and a BMI of 30 kg/m2 or above indicates obesity in white men and women of all ages, according to World Health Organisation's (WHO) categorisation system.
However, some research has found that this classification system may not be good at identifying overweight and obesity in athletes and its use in this group has long been subject to criticism.
"BMI doesn't distinguish between body fat and lean mass, which includes muscle," explains Professor Marwan El Ghoch, of the Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy. "As a result, a muscular athlete with low body fat can be wrongly classified as living with overweight or obesity. Despite this, many sports organisations still rely on the traditional BMI classification system."
In a new study, Professor El Ghoch and researchers from the University of Verona in Italy and Beirut University in Lebanon set out to determine how accurate the BMI cut-offs of 25 and 30 kg/m2 are at identifying overweight and obesity in male athletes and, if they were found to be inaccurate, to establish better cut-offs.
The cross-sectional study involved 622 males (average age of 25.7 years, BMI ≥ 20 kg/m2) who had been referred to the Department of Neurosciences, Biomedicine and Movement Sciences, of the University of Verona, Italy, and participated in sports including soccer, rugby, basketball, volleyball, cross-fit, karate and others at a competitive level.
The participants were categorised using the current BMI system and by their body fat percentage (BF%).
Using the current BMI system, more than a quarter of the individuals were categorised as living with overweight or obesity. Some 451 (72.5%) individuals were of normal weight (BMI 18.5-24.99 kg/m²), 148 (23.8%) individuals were with overweight (25 kg/m²-29.9 kg/m²) and 23 (3.7%) were with obesity (30 kg/m² and above).
Total body fat percentage (BF%) was measured using dual X-ray absorptiometry (DXA) scans – known to be a highly accurate tool for measuring body composition – according to age- and gender-specific cut-off points. A BF% of 21% or above was classified as overweight and a BF% of 26% or above was classified as obesity.
Using this system, fewer than 4% of the individuals were categorised as living with overweight or obesity. Some 598 (96.1%) individuals were of normal weight, 19 (3.1%) were with overweight and 5 (0.8%) were with obesity.
Professor El Ghoch, who led the study, says: "This demonstrates that the current BMI cut-off points are clearly flawed in determining weight status in athletes, as many of the athletes were misclassified as living with overweight or obesity, where in reality, very few had body fat levels in this range."
The researchers went on to use statistical modelling to identify more accurate BMI cut-off points for young male athletes. The new cut-offs, which take into account athletes' lower BF%, are 28.2 kg/m2 for overweight and 33.7 kg/m2 for obesity.
Study co-author, Professor Chiara Milanese, of the University of Verona, explains: "Although DXA scans measure body composition accurately, they are not always available in sports settings. In contrast, weight and height, the two measures needed to calculate BMI, are easy to obtain and, with the new BMI cut-offs that we identified, BMI could be a highly useful tool in sports clubs, both at training grounds and in competitions.
"A direct assessment of body composition remains the gold standard but, in its absence, we encourage sports organisations and committees to adopt the new BMI classification system."
The authors add that several further pieces of research are needed. These include identifying new cut-offs for female athletes and, potentially, specific cut-offs for different sports, particularly those were not included in the current study.
