Why BMI Can Be Misleading for Athletes
Athletes and regular exercisers often have higher muscle mass, which increases body weight without increasing health risk. A BMI of 26-28 in a trained individual may be perfectly healthy. Use this calculator to get your BMI, but interpret it with the context of your training level.
If you train seriously, your BMI is almost certainly misleading. BMI divides weight by height squared, but it cannot distinguish between 10 kg of muscle and 10 kg of fat. A rugby player, a CrossFit athlete, and an obese sedentary person can all have the same BMI while being in completely different states of health. Studies show that up to 30 percent of people classified as overweight by BMI actually have a normal or even low body fat percentage. For athletes, body fat percentage, DEXA scans, or skinfold measurements give a far more accurate picture. That said, BMI still has value as a screening tool when combined with other metrics. If your BMI is high and your waist circumference is also above average, the excess weight is likely fat rather than muscle. If your BMI is high but your waist is lean and you train regularly, you can safely disregard the overweight classification.
- Ask your gym or doctor for a body fat measurement using calipers or a DEXA scan. These methods are far more useful for athletes than BMI.
- If your BMI reads overweight but your waist is below 94 cm (men) or 80 cm (women) and you train hard, the number is simply reflecting muscle mass.
- Endurance athletes like marathon runners often have a low BMI but can still have metabolic risk factors. Don't assume a low BMI means perfect health.
- Use BMI as one data point among many. Resting heart rate, blood work, and performance metrics tell you much more about your fitness and health.
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