Why Your BMI Is Completely Meaningless (And What to Measure Instead)

Clients often come to me with a single goal: to lose weight and lower their BMI. Today, I am going to try to convince you why relying solely on the number on the scale is not a good indicator of your weight reduction.

What is BMI?

Body Mass Index (BMI) is a body weight indicator that allows for statistical comparison of body weight. BUT! Why doesn't BMI make sense sometimes? Take an athlete, for example—10% body fat, muscle mass well above average... yet their BMI places them in the category of class 1 obesity. Why is that?

The calculation itself gives us the answer: 

BMI works with only two data points—weight and height. It doesn't ask how much of your weight is muscle. It doesn't ask how much fat you have, or where that fat is located. It doesn't ask about your fitness level, your diet, your metabolic health, or any potential health risks.

Same BMI, Two Completely Different Bodies

Imagine two women—both are 168 cm tall and weigh 70 kg. Their BMI is approximately 24.8 (the upper limit of normal). At first glance, the numbers look identical, but their bodies can have completely different compositions.

• Woman A – regularly goes to the gym, has well-developed muscle mass, a relatively low body fat percentage, a 72 cm waist circumference, good physical fitness, and normal metabolic parameters.

• Woman B – has significantly less muscle mass, a higher percentage of body fat (especially in the abdominal area), gets little physical activity, and has lower overall fitness.

Both women have the same BMI, yet their body composition and health risks are entirely different.

Does this mean BMI is useless?

Not necessarily; it has its place in healthcare. It is simple, fast, and can be useful when evaluating large groups. However, the problem arises when we turn it into a verdict on an individual.

When we look at a person from a nutritional perspective, we are interested in a much broader picture, such as:

• Body composition – muscle mass weight, distribution of fat tissue, etc.

• Dietary habits

• Weight history

• Physical fitness

• Selected laboratory values

• Health issues and limitations

• And above all, the overall health and lifestyle context of the individual

That is why aiming to increase muscle mass, reduce visceral fat, and improve overall fitness makes much more sense than simply saying, "I want to get my BMI down to 25."