Body mass index (BMI) greatly overestimates overweight and obesity in athletes, according to a study at the European Congress on Obesity (ECO 2025, Malaga, Spain, 11-14 May). The team from Italy proposes new cut-off points for this group.
Body mass index (BMI) is a way to assess people’s weight status, defining whether they are normal weight, overweight, or obese. It can be easily calculated by dividing an individual’s weight (in kilograms) by the square of their height (in metres). According to the World Health Organisation’s (WHO) categorisation system, a BMI higher than 25 kg/m2 shows overweight, and a higher than 30 kg/m2 shows obesity.
However, there is some criticism about using this classification system to identify overweight and obesity in athletes. “BMI doesn’t distinguish between body fat and lean mass, which includes muscle,” explained 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 this study, a team of researchers from the University of Verona in Italy wanted to determine if the BMI cut-offs of 25 and 30 kg/m2 can identify male athletes who are overweight or obese. Over 600 participants from multiple sports, including soccer, rugby, basketball, volleyball, cross-fit, and karate, participated in the study.
Using the current BMI system, about ¾ had a normal BMI, but 23% would be considered overweight (BMI between 25 kg/m²-29.9 kg/m²), and about 4% would be classed as obese (BMI 30 kg/m² and higher).
The team also compared total body fat percentage (BF%) using dual X-ray absorptiometry (DXA) scans. In this case, a BF% higher than 21% was classed as overweight, and a BF% higher than 26% was classed as obese. Using this system instead of the BMI, less than 4% of the individuals were categorised as overweight or obese. Most athletes were within the normal range; 3% were overweight, and less than 1% were obese.
“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,” said Professor El Ghoch.
Based on these results, the team went on to use statistical modelling to more accurately identify the BMI cut-off points for athletes. According to the authors, the new cut-offs, considering lower BF% for athletes, should be 28.2 kg/m2 for overweight and 33.7 kg/m2 for obesity.
“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,” said Professor Chiara Milanese, of the University of Verona. “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 now want to identify specific cut-offs for female athletes and even specific cut-offs for different sports.