It's easy to think the number on the scale is the ultimate indicator of our health and fitness progress, and we often fall into the trap of using the Body Mass Index (BMI) as a reliable measure. However, BMI (like body weight) is an old and simplistic tool that, while it can give a rough idea at a population level, doesn't accurately reflect the reality of your body composition or overall health.
What is BMI?
The Body Mass Index (BMI) is a mathematical measure used to classify people into categories such as underweight, normal weight, overweight, and obesity, based on their weight and height. It is calculated by dividing weight in kilograms by the square of the height in meters (kg/m²). This figure can be useful for epidemiological studies or to get a general idea of the nutritional status of a population. Although it is an easy and inexpensive tool, the BMI does not directly measure body composition, so it can be misleading at the individual level.
Limitations of BMI
- Does not distinguish between muscle and fat: A person with a large muscle mass may have a high BMI and be mistakenly labeled "overweight" or "obese," despite being in excellent physical shape. This is particularly common among athletes and gym enthusiasts.
- It ignores body fat distribution: The location of fat, especially visceral fat, which accumulates in the abdomen, is a key factor in the risk of cardiovascular and metabolic diseases. BMI does not differentiate between subcutaneous fat (less harmful) and visceral fat (more dangerous).
- Does not consider individual differences: Factors such as age, gender, and ethnicity can influence body composition and health risks, but BMI is used in a consistent manner for everyone.
- Measure aimed at population statistics: Its usefulness lies in large-scale studies, not in individual follow-up.
Alternatives to measure your progress and health
To get a more accurate picture of your physical condition and the changes you experience, it is necessary to replace the BMI with other more specific and comprehensive measurements:
- Body composition measurements:
- Electrical bioimpedance: Many modern scales offer estimates of body fat percentage using a low-intensity electrical current.
- Skinfold measurements: Using calipers to measure skinfold thickness at specific sites to estimate subcutaneous fat.
- DEXA or dual energy X-ray absorptiometry: While these methods are more expensive and less accessible, they provide a detailed assessment of fat, muscle, and bone density.
- Waist circumference and waist-to-height ratio:
These measurements are excellent for assessing visceral fat and have been shown to be better predictors of cardiometabolic risks than BMI. An increase in abdominal circumference may indicate a higher risk of health problems, even if BMI remains within a "normal" range. - Physical performance evaluation:
Progress in the gym isn't just reflected in your body weight. Monitoring improvements in strength, endurance, speed, and flexibility gives you a more realistic picture of your fitness progress. - Progress photos and body measurements:
Comparing photos and taking measurements (such as arm, waist, hip, and thigh circumferences) can help you visualize changes in body composition, even if the scale doesn't show significant changes. - Comprehensive health indicators:
Monitoring other parameters such as blood pressure, glucose levels, cholesterol, or overall well-being allows you to assess your health from a holistic and functional perspective.
Conclusion
While BMI can be an easy and inexpensive starting point for classifying weight status at a population level, it's not the ideal tool for assessing your personal health or your progress in the gym. The scale and the BMI number don't distinguish between muscle and fat, nor do they reveal where that fat is located on your body. It's essential to adopt a comprehensive approach that combines body composition assessments, anthropometric measurements, and tracking physical performance and health parameters. Only then can you get a true picture of your well-being and adjust your habits to achieve your goals in a healthy way.
Adopt a tracking approach that goes beyond just the number on the scale, and you'll see how every effort you make in the gym translates into real improvements in your health and quality of life.